Petrie is hopelessly confused

DiddyKF1 · **on:** February 20, 2018, 07:21:57 PM

Poor Petrie. Never seems to be able to make a decision on his own.

Petrie: Uuuuummmmmm, ... why me no can think with so many distractions!?

Littlefoot505 · **Reply #1 on:** February 20, 2018, 09:52:05 PM

He's trying to take the derivative of a function using the limit definition.

Flathead770 · **Reply #2 on:** February 21, 2018, 12:51:14 AM

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He's trying to take the derivative of a function using the limit definition.

Oh no

I don't even fully remember how to do that since you never use it after you learn the shorter method. It's something like Lim as h->0 of [f(x+a) - f(x)]/h right?

To continue the math trend, this would also be his expression when first learning integration by parts.

Littlefoot505 · **Reply #3 on:** February 21, 2018, 10:16:56 AM

Quote from: Flathead770 on Feb 20 2018, 11:51:14 PM

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He's trying to take the derivative of a function using the limit definition.
Oh no I don't even fully remember how to do that since you never use it after you learn the shorter method. It's something like Lim as h->0 of [f(x+a) - f(x)]/h right?

I had to take a lot of derivatives using the limit definition for my Calc 1 class. I even had to do it a few times after learning the shortcuts! I actually learned two different formulas for it. One of them I think is lim as h->0 [f(x+h)-f(x)]/h, and the other one was something like the one you said, but I’m not sure exactly what it was. I never got the hang of either of them

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To continue the math trend, this would also be his expression when first learning integration by parts.

Gee, that’s reassuring! I just started Calc 2, so I’ll probably be doing that soon.

Flathead770 · **Reply #4 on:** February 21, 2018, 07:41:24 PM

Ah ok. No your way makes more sense having f(x+h) instead of some arbitrary a in there. Remember (or at least I should remember

) that the definition of a derivative is the slope of the tangent line to a curve. The slope is the change in y ( f(x+h) - f(x) ) over the change in x ( x + h - x = h ). To get the slope of the tangent the change in x has to shrink smaller and smaller until it is infinitesimal which is why we take the limit.

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Gee, that's reassuring! I just started Calc 2, so I'll probably be doing that soon.

More then likely. I "learned" it in my second calculus course. My prof. was pretty bad though and no other course required it until I finally learned it for good in Quantum Mechanics, so it only took me a few years

The Chronicler · **Reply #5 on:** February 22, 2018, 10:01:18 PM

Caption:
Petrie's response to the previous comments...

"Me no understand anything you guys talking about!"

Littlefoot505 · **Reply #6 on:** September 24, 2018, 10:54:48 PM

^ Lol nice one

Shifting from math over to chemistry, this probably would also be him when he first learns how to balance a redox equation

ImpracticalDino · **Reply #7 on:** July 05, 2019, 10:26:00 PM

My reaction to everything that has been said here in a nutshell.

I only have experience in Algebra and Geometry so far.

I also have to question, how did all of you still remember the stuff you learned back in school? Unless it's something important, I'd expect you to forget everything by now.

Well...you could still remember a few things here and there.

-b +/- the square root of b^2 - 2ac divided by 2a? Let's see if my memory of the quadratic formula was right...

Well, almost. I searched and found out it was -4ac, not -2ac. Pretty good overall though.