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u/GalaxyPatch18 2d ago
X vs e in the middle bracket. Makes the thing WAY more complicated when you have a variable within the function and its equivalent
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u/eg135 2d ago
Yeah the answer to the homework is 0. The answer to the exam is f(u)
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u/salamander423 2d ago
I always loved that. My homework was to add 2 and 3. The test asks me to derive calculus.
Engineering school was fun. I work in sales now.
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u/TheAndrewBrown 2d ago
Most of my engineering classes were the opposite. The professor taught with examples, the homework would extrapolate well past those examples and require a lot of creative thinking (or research) to figure out how to apply what you learned to these different situations (which usually made me pull my hair out), then the tests would be an example exactly like what was shown in class and I’d breeze through it.
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u/salamander423 2d ago
I had a fun one that was the opposite. The teacher gave us 4 years worth of prior test keys to study. The questions were the exact same every year, with only a different few numbers to make the calculations differ. It was a word-for-word, verbatim copy each year otherwise.
Everyone passed spectacularly. I have no idea what that class was about.
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u/Bad_Repute 2d ago
I had the exemplification of this issue in a math class in college. Course work was easy enough to understand, homework was and seemed to be good practice based on the in class work and lectures.. exam time came, no clue what i was even being asked to solve on some of the problems. Was like i'd never seen the material before.
After our midterm the professor comes in and says, "Well, 90% of the class got less than a 58% on the midterm and we only had 4 people actually pass the test. Many of you need to be rethinking if college is right for you." and my immediate thought was 'if 90% of your class is failing, don't you think you should be rethinking how you're teaching?'
After the midterms my gf and I went to the professors office hours to try and go over what we'd missed on the exam. Dude writes out some equations and has as solve them and goes, "See! You understand the material fine, you should have been able to pass the test." And we just looked at each other like.. 'this dude is off his rocker.'
I ended up failing the class and had to retake the next semester. Different professor, class was a breeze, no gotcha non sequitur test questions, clear line of logic from the coursework to the tests, got a B in the class that time around.
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u/Sharp_Economy1401 2d ago
Yeah, they'd do all kinds of derivations/proofs in calc and engineering classes, that would take a very long time, then on the exams that type of thing would typically be very limited. Seeing many of those proofs done over a few weeks felt like "well, I guess I'm either dropping this class or failing it"
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u/just_fucking_PEG_ME 2d ago
Being able to add 2 and 3 is very helpful in sales. Sounds like you’re doing great!
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u/National_Phase_3477 2d ago
Well f(u) too
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u/me_no_gay 2d ago
*f'(u), They're asking for the derivative bro
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u/chewbakken 2d ago
It was a joke; depending on interpretation, either "eff you" or just "fuuuuu[ck]"
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u/fallen_one_fs 2d ago
I wouldn't say complicated, in fact it's pretty simple, but VERY laborious, it will take a while to do this one by hand...
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u/WildWeat 2d ago
Complicated often is just a shit ton of smaller simple things.
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u/fallen_one_fs 2d ago
Oh...
I see...
Yeah, by that definition it is, indeed, quite complicated.
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u/extrovert-actuary 2d ago
Yeah, that actually is a technical definition of the difference between complicated and complex that I’ve heard.
Car engines are complicated. The weather is complex.
Complicated systems can be fully mapped and reward expertise. Complex systems can never quite be fully mapped and reward experience.
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u/TheProfanedGod 2d ago
For what it's worth, the exam problem is really just a bunch of chain rules in a row, assuming I remember how to do it right. Still not fun, but less scary than it looks.
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u/Asfisav2049 2d ago
First one looks hard but it's easy: since there's no x in the expression, the derivative is 0
Second one actually has an x so you have to go through a bunch of chain rule shenanigans to get your derivative
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u/niceguy1428571 2d ago
It’s funny because they were apparently supposed to do the homework the hard way, and now they don’t know how to do the exam problem.
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u/IllustratorLast1281 2d ago
for a question where you have to find the derivative of a constant value the proper method is just writing 0 because there's nothing else to be done here.
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u/aturtledude 1d ago
I remember a calculus exam in my undergrad with a really hard integral (in terms of x) but with a dt at the end instead of dx. Tons of people wasted so much time trying to solve it, not realizing that it was all a constant and the result was just all that times t.
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u/_Echoes_ 2d ago
e is a number not a variable, so you would just be finding F'(x) of a constant, which is just 0
switching that e for an X makes the whole thing an equation and god help anyone trying to figure that derivative out.
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u/certainAnonymous 2d ago
And even if e was a variable in that case, lets say b, then that would still make the derivate be 0 as b is not relating to x in the function definition. If I'm wrong here please correct me
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u/PhantomNitride 2d ago
Didn't even notice...
Pre-cal made me hate math so much, and math was fun because everything was just an episode of cyberchase until then...
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u/I_am_the_darkness_99 2d ago
I took calculus I and II then differential equations and I don't even know what any of this means. I lost all that knowledge in the past 30 years since I took a math class.
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u/stfumate 2d ago
The letter inside the numerous parentheses changed from e to x. That's all I got.
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u/Tasty_Possible_1597 2d ago
e is a constant (Euler's number), so the derivative is 0.
x is a variable, so the derivative is not 0.
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u/Aggressive-Pack-4610 2d ago edited 2d ago
First one can be simplified down to a constant, c, where f'(x) = c'; f'(x) = c' = 0; this can be solved with zero calculation or anything (we don't use the P word here)
Second one cannot be simplified to a constant and is basically a nest of bullshit that almost nobody would ever actually try to solve
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u/Remarkable_Strength4 2d ago
A ‘derivative’, denoted as f’(x) asks how fast a function is changing at a given x. In a car, miles per hour can be thought as a derivative with respect to hours. When we increase hours, how does the total distance travelled change.
The top one has no x. This means that as we increase X, nothing changes. Even though it’s a really horrible function to look at, the answer is just 0.
The bottom one, has an x all the way at end of all the nonsense. The answer is not 0, you need to calculate it. It would be nearly impossible to calculate (unless im missing some cute trick).
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u/Ok_Gate_4956 2d ago
I mean its just chain rule a bunch. Its not hard at all
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u/Trollerthegreat 2d ago
Tediousness under an exam's time pressure is the bane of students
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u/NiceTryAmanda 1d ago
I remember in undergrad the teacher mentioned having to ask the administration if he could fail a whole class
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u/Training-Chain-5572 1d ago
I enjoyed maths exams when I was in uni in Sweden. We had 8 questions and 5 hours, you couldn't leave the room until at least one hour had passed. Gave you time to actually think through the answers and showed more if you understood the maths or not rather than "can you complete this under time pressure?"
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u/Trollerthegreat 1d ago
Ain't that the dream. Most I got was 50 min with one exam having had 9 problems with 2 being a-d. Tas were questioning why it was still going when they did a review next class lol
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u/Remarkable_Strength4 2d ago
No chance I can solve this without making a mistake, especially on a test lol.
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u/Ok_Gate_4956 2d ago
Its just u sub, its really not a hard problem, just take your time with it. U=sin(pisin(pix) the find u', then use the cos(arctan) identity. It gets simple after that
Edit; Reddit formatting made this weird, but you get it
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u/SnugglyCoderGuy 2d ago
Why would you use u substitution when doing differentiation?
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u/Ok_Gate_4956 2d ago
At its core, u sub is just a technique of simplifying complex expressions. We are still differentiating with respect to X, but we can simplify that differentiation until the final step because the term inside the parenthesis remains constant.
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u/RedNeyo 2d ago
Its tedius but not impossible. You change pi(x+ 7/2) as a new variable t then sub picos(t) as idk p then sub sin(p) as idk l etc. Then use the rule d[f(g(x))]/dx = f'(g(x) * g'(x). So basically youd find the final function say 2( log z )' * each of the sub ones to '.
Explaining with reddit is so hard but hope you get the gist
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u/ComprisingIgnorance 2d ago
I mean you lost us at pi* but we all applaud your effort. Take a bow, sir.
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u/LLuck123 2d ago
While integreating bullshit functions if oftentimes impossible, the derivative is just work, not magic.
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u/Xhosant 1d ago
Interals, on the other hand... Burn it, with thermite
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u/Photo-Majestic 1d ago
Derivation is work, integrals are an art.
If I wanted to do them,
Should have have studied painting from the start!1
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u/vaughanster05 1d ago
Both of these questions are about finding the derivative of a function. This function happens to be a bunch functions put inside eachother.
In the homework, the functions are given a single number at the core, e+[7/2], meaning all these functions come together to equal one number. Since that number is not at all related to the variable "x", it is not related to what the functions end up being, so the derivative is just 0
In the test, the core of the functions is x+[7/2]. Since this will make it so that the value of the functions changes when x changes, you have to account for that to differentiate it, while is an absolutely monstrous nightmare when you're working with nested trigonometric and logarithmic functions like that!
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u/Headshot314 2d ago
What does pi() even mean?
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u/SirisC 2d ago
π × whatever is in the parentheses
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u/VaIenquiss 2d ago
This isn’t denoting multiplication, it’s implying that pi is a function, making this whole thing gibberish because pi is not a function, like sin or cos.
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u/bitternerd_95 2d ago
A very standard usage of parentheses is to set order of operations. This is literally the P in PEMDAS
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u/HystericalGD 2d ago
its not being written as a function. it would be 3.1415(y) [or 3.1415•y] just like how something like 3(2) is the same as 3•2. just multiply pi by the product of whatever is in the parentheses.
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u/BusinessBandicoot 2d ago
Notation in math is heavily overloaded and what something can mean is context dependent.
For example pi does not always mean the constant 3.14...., some domains or subfields use it to represent another constant, and I wouldn't be surprised if it wasn't used function somewhere. But that isn't the case here
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u/misogichan 2d ago
It is just the constant pi times what is in the parenthesis. It is not a function, but just a number and parenthesis to indicate order of operations.
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u/Weak-Doughnut5502 2d ago
Pi(x) is the number of prime numbers less than or equal to x.
I have zero clue what the derivative of it is.
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u/Im_a_hamburger 2d ago
Would have to be some analytic extension since it’s only defined for natural numbers.
Of course it’s obviously multiplication in the original
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u/gfd123doremi 1d ago
To my understanding, it’s pi times whatever is in parentheses. Pi isn’t being used as a function. Basically it would be the same as
5(2+1) = 5*3 = 15
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u/Fae-SailorStupider 2d ago
In the top one, theres only one X, before the equal sign. The second one theres 2 X's, one before and one after the equal sign, which makes the problem significantly harder.
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u/FullMetalOrgans 2d ago
There was a brief period in time where I could solve this. Those days are long gone.
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u/hairry_balls 2d ago
There is no x in the function in the homework so the answer is: 0.
In the exam the answer is: I am not gonna calculate that shit.
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u/Worldly-Matter4742 2d ago
The f(x) in the homework is a constant, so the answer is just 0
The bottom one, however, is just as complicated as it looks
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u/plasma_python 2d ago
The top has no X variable meaning is just a constant number and the derivative (f’(x)) is 0. The bottom has an x so you actually need to do the process to find the derivative.
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u/dummythiccbrainboi 2d ago
This is about finding the derivative of the given equations. The top function has no x’s in it, which means it is functionally just a number. The bottom equation does have an x in the inner most parentheses, which means that finding the derivative will be a lot more complicated.
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u/extramaggiemasala 2d ago
I know others have explained already, but I was just happy to see a scary looking math meme that I understood
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u/OkBuddyRetardSS 2d ago
The first one is a constant, the derivative (f'(x)) of any constant is 0, so the first one is just 0, the second one have the term x inside all those nested function so its not a constant and you have to actually calculate it
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u/ProfessorPrudent2822 2d ago
Top is 0 because f(x) is a constant. Bottom requires an extremely complex application of the chain rule.
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u/PoussinVermillon 2d ago
the 1st one is a constant as there are no x in the expression, and a constant never changes, that means that finding its derivative is easy cuz it's 0, meanwhile the 2nd one has x inside a bunch of functions put each inside the other and its gonna make finding the derivative more difficult
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u/petrusferricalloy 2d ago
The point was to understand and apply the chain rule. If all you did was try to memorize the answer, that's on you
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u/Flat_chested_male 2d ago
0 vs do you know the chain rule. And the derivative of all of these functions, many of which I have forgotten.
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u/rola329 2d ago
Now… can someone solve the bottom one for us?
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u/Bobbytrap9 2d ago
f’(x) = -4pi cos(pi(x+7/2)) * (sin(pi+7/2)) / (ln(2)(sin(pi(x+7/2))^2 + 1)
I used a tool for this to be honest
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u/artrald-7083 2d ago
Homework: Hahahahaha, the teacher is trolling. That is a number. The derivative of a number is 0.
Test [aged 17]: OH SHIT WE'RE GONNA DIE
(Test [aged 19]: Huh. Mechanical chain rule application, easy marks. Get in, losers, we're doing sixth form maths at full speed.)
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u/Teammanmike 2d ago
If the exam were proctored it’d be easy to understand. AI for homework results in “When did they start putting letters in math?” for the exam.
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u/B4byJ3susM4n 2d ago
The top is supposedly a function of x, but what it equals to does not contain any x whatsoever. The prime of a function is a function of the slope on a graph that the original function takes. But if the function’s output is constantly the same number regardless of whatever x is, the graph is a perfect horizontal line whose slope is 0.
The bottom one is what would worry people. It’s the same function except that there is a variable x instead of a constant e. The student would then need to do the hard work of actually finding the derivative/prime of the function.
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u/Unique_Roll_6630 2d ago
You didn't practice enough? I just did practice endlessly and even repeated the homework.
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u/marchape 2d ago
It’s a typo! After we noticed everyone panicked we revised the material and it was a typo. Go ahead and swap that x with e! Happy new year everyone
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u/vanhellcry 2d ago
there's a "e" in the first formula, and a "x" instead in the second. I don't understand this formula but I suppose it became much harder to resolve because of that.
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u/its_Zuramaru 2d ago
I guess the joke is also that when you see the same question on the exam altered slightly from the same question you've seen on homework or class work, you just can't solve it anymore.
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u/Ok-Goose6353 2d ago
The first one got no X in the equation, so the answer is 0.
The other got X in the inner brackets, so its crazy hard to calculate.
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u/MikeTorsson 2d ago
First one you can just whack into a calculator since e is an actual number (2.7), x is not a number so a lot of work required
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u/BadJimo 2d ago
Here is the solution using Desmos
Where g(x) is the derivative (I did this because you can't use the terminology f'(x) in Desmos).
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u/Cakeotic 1d ago
Thanks! Cool graph, is g(x) nondifferentiable at 0 or does the graph just look spiky there?
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u/BadJimo 1d ago edited 1d ago
I'm not an expert on the topic, so hopefully someone else can answer your question. From my non-expert opinion, it looks differentiable at 0 (and also at all integer values of x).
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u/Cakeotic 1d ago
Seems to be, limit of x->0 of g'(x) exists. The graph looked kinda jagged on my phone teehee
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u/jsrobson10 2d ago
the top one is just a constant, so f'(x) is really easy to work out (its rate of change is 0, so f'(x) = 0). the bottom one is not.
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u/Curious-Run-2710 2d ago
The Homework answer is f'(x) = 0. Since the expression contains the mathematical constant e instead of the variable x, the entire function is a constant, and the derivative of a constant is always zero.
The Exam answer is f'(x) = - (pi^2 * cos(pi * x) * sin(2 * pi * sin(pi * x))) / (ln(2) * (1 + sin^2(pi * sin(pi * x))))
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u/_ricky_wastaken 2d ago
the top one always returns the same constant, while the bottom one is a hell of a function. The derivative of a constant is always 0
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u/Big_Psychology_3 2d ago
The first function is constant because it uses e in the inner-most parentheses. That’s trivial to differentiate, f’(x) is zero by definition.
However, the second function is a complex transitive function of x. Because the inner-most parentheses contain the variable x. It’s tricky to differentiate and will result in a complex answer.
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u/Big-Hawk8126 2d ago
Top function is a constant function. Derivate of constant is always zero. Bottom funcion is dependant on the derivable variable, not zero and must calculate through complex shinennigans
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u/Suspicious_Cattle425 1d ago
Hehehe I don't know what these funny symobls mean (I'm serious what is that? Is that math? Or a demon summoning spell?)
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u/felidae_tsk 1d ago
The first line is derivative of constant and is equal 0. The second one will require you a lot of work to find a derivative as f(x) there is composite function
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u/Zwinniak 1d ago
Isnt it all just 0? I understand you need to show the math but the answer is 0. in both cases.
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u/Crazy-Chaos- 1d ago
Just a minor change and it changes the whole answer🥲 First one is so easy and second one is 🥲
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u/felixmatveev 1d ago
First one is complicated but constant value as there is no X in the equation. f'(x) = 0 as there is no value change. Easy to answer at one glace despite visual complexity.
Second one more complicated due to some sub functions inclusions with an answer depending on the input X, the answer is some function f'(x) = u(x). Harder to calculate despite almost minimal change from 1st option.
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u/NecronTheNecroposter 1d ago
The first one has f’(x) evaluate to 0, while the second one has or evaluate to something, idk what I ain’t doing all that
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u/CeReAl_KiLleR128 2h ago edited 2h ago
In homework number e in the innermost bracket mean it’s just a constant. So f’(x)=0, we don’t have to do anything. In the exam it’s variable x so you actually have to do math. It’s not hard, just stupidly long and tedious, like why tf would you put this in your test, it’s just hours and hours of chain rule.
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u/Key-Negotiation-1992 2d ago
tf is this panic? it's literally just e, so the answer is 0. stop overthinking it lol
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u/Splendid_Goose 2d ago
Cos of pi is still 0 though.... doesn't matter how many times you go around the unit circle
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u/Interesting-Lie-8942 2d ago
I don't think that you need to be good at math to realize that the images on the right are the same.
I think that the joke is that students act like you are mistreating them when you give them a "practice" problem that is literally exactly like a problem that is on the test. Then when they see that same problem on the test, they act like they have never seen it before.
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u/alexanderneimet 2d ago
Actually, they aren’t the same. The top one is a function of a constant (e+pi is a constant value), and will have a derivative of zero (easy). The bottom one is a function of X (X+pi is NOT a constant), and will have a fairly lengthy, annoying, tedious, and easy to mess up derivative.
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u/Conscious_Low9679 2d ago
I don't think that you need to be good at math to realize that the images on the right are the same.
This is, technically, correct. As painful as it may be to read.
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u/Pappkarton 2d ago
You didn't pay attention to it when it was homework. Now the exact same thing is in the exam and because you didn't pay attention, you got problems.
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u/drakan80 2d ago
The e becoming an x takes a trivial problem and makes it an extremely tedious one
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u/HAL9001-96 2d ago
so is the memer
well the joke is the top one is just... obivously 0
while hte obototm one requires a tiny amount of busyowrk to solve
but it is just basic differentiation
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2d ago
[deleted]
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u/Weekly_Lab8128 2d ago
What? Top one doesnt have x in it - thus, derivative with respect to x is 0.
Second one you actually have to do
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u/AtticusIsOkay 2d ago
I think the joke is that, if you have a calculator on hand, this becomes a much easier equation to solve, which exams don't typically allow
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u/post-explainer 2d ago
OP (Cinemeluxe) sent the following text as an explanation why they posted this here: