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I'm bored so I'm sharing what I believe is a neat proof for something useful. What you need to know to understand this is derivatives, compositions, and a bit of algebra (I think).

Let g(x) be the functional inverse of f(x).

Using knowledge about functional compositions, I can determine that f(g(x))=x.

Taking the derivative of both sides...

ddx(x)=ddx(f(g(x)))

Solving the derivatives...

1=f(g(x))g(x)

Dividing both sides by f(g(x))...

f(g(x))1=g(x)

f(g(x))1=g(x) is a simple method that allows an indirect derivation of an inverse function.

Example problem:

f(x)=2x2

f(x)=2x2+1xln(2)

g(x)=log2(x)

12log2(x)2+1log2(x)ln(2)=122log2(x)log2(x)ln(2)=12xln(2)log2(x)=12xln(2)ln(x)

Now checking the actual derivative of the function I get g(x)=12xln(2)ln(x)

I'll upload more proofs when I'm bored again.

 
 Feb 21, 2019
edited by creepercraft97T3  Feb 21, 2019
edited by creepercraft97T3  Feb 21, 2019

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