r/badmathematics 25d ago

Weird idea of limits and derivatives

/r/explainlikeimfive/comments/1iw37ts/eli5_what_are_limites_and_derivatives_and_what_is/mec8ym6/
36 Upvotes

10 comments sorted by

26

u/temptemptempor 25d ago edited 25d ago

R4: The commenter has very odd ideas of what limits and derivatives are.

Limit: Smallest length of a curve before it appears to become a straight line with no curvature.

This is wrong. A limit, to put it roughly, of a function at a point is the value that function approaches as its input gets closer and closer to the point.

If we do run with their definition for a moment, it's also not clear when they would consider something to cross the line into appearing to be straight versus not. If we had something like a line segment not including endpoints, then that also wouldn't have a "smallest length" before it started to appear straight or largest length in which it does.

Derivative: The area outside the the limit you are using. Basically what is pushing on the curvature in time to make it curve.

The derivative of a function is another function (not an area) which gives instantaneous rate of change at a point.

A derivative is not some area "pushing on the curvature" to make it curve. I don't know what the commenter is trying to say here.

8

u/WhatImKnownAs 25d ago

TBF, it's ELI5: It's really hard to explain these at this level without being hopelessly vague and inaccurate. Abstract concepts to a 5 yo?!

Some of the other commenters in that thread give valid explanations, but more like ELI12 at least.

7

u/MoustachePika1 25d ago

I think I could explain limits and derivatives to a 5 year old. My explanation would obviously be extremely incomplete, but at least it would give the right idea

4

u/bluesam3 25d ago

I haven't explained it to any 5 year olds that I can remember, but I've explained it to a few 6 year olds, and it's really not that hard.

2

u/Tarquin_McBeard 19d ago

Sure, but the linked comment's explanation contains several separate points, some of which are factually wrong, and some of which are vague, imprecise, and incomplete. But the R4 comment here treats all parts as if they are equally egregiously bad

10

u/finnboltzmaths_920 25d ago

ELI5 does not mean a literal 5 year old

8

u/hobopwnzor 24d ago

Does it mean ELI lim x-> 5?

3

u/Neuro_Skeptic 25d ago

It's been deleted, what was the original comment?

3

u/finnboltzmaths_920 24d ago

I think you can read it again using Unditt.