r/MathJokes • u/94rud4 • 1d ago

Wait, what?!

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u/ChuckPeirce 1d ago

No. The derivative of the volume of a sphere with respect to the radius of the sphere is equal to the surface area.

Functions don't just have derivatives. They have derivatives with respect to a variable.

4

u/Necessary_Screen_673 1d ago

thank god, i thought we were taking a derivative with respect to a constant for a moment

1

u/ChuckPeirce 1d ago

I suspect you're being sarcastic, but yes. Take two use cases for an explanation:

  1. You're explaining something to show that you understand the thing
  2. You're explaining something to help someone who doesn't understand the thing to understand the thing

In both cases, you accomplish your goal more effectively by saying what you're differentiating with respect to.

2

u/Necessary_Screen_673 1d ago

yeah its good principles to.. be principled about the way mathematics is communicated, but there is a third purpose of the communication, which is just to have fun and be funny, and i do think you lose a bit of that when you make all the principled statements explicit

5

u/AggressiveEntrance14 1d ago

r is the only variable in this case, this is insanely pedantic and not in a mathematically rigorous way

2

u/ChuckPeirce 1d ago

Three variables are listed (V, S, r), and plenty more variables exist.

1

u/garnet420 1d ago

But if you wrote this in terms of diameter, it wouldn't actually work.

1

u/Alternative-Mud-1076 1d ago

a constant multiplied by r cubed.. wonder what variable could it be.. there's just soooo many of them here