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submitted 9 months ago by [email protected] to c/[email protected]
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[-] [email protected] 13 points 9 months ago* (last edited 9 months ago)
  1. f is a real function from the xy plane to the reals
  2. draw a horizontal-ish band (that is, two lines) creating your favorite wobbly band shape
  3. the integral of f along a single vertical line within the band is itself a function of the line's x coordinate. Call the function g(x)
  4. What is dg/dx in terms of df/dx? lf the band were perfectly horizontal, it would just be the integral along the vertical line of df/dx within the band. But it's not, so you add a term to account for the band lines moving
  5. all this assuming f and the band are pretty enough (this is 80% of the theorem statement)
[-] [email protected] 2 points 9 months ago

For number 4 (or maybe a new number), if a(x) and b(x) are constant, the derivatives d/dx a(x) and d/dx b(x) are zero, so all that is left is that d/dx becomes a partial derivative and can move inside the integral.

[-] [email protected] 10 points 9 months ago
[-] [email protected] 6 points 9 months ago

Leibnitz nuts

this post was submitted on 06 Oct 2023
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