Integrating using inverse functions
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Someone the other day told me about the idea of evaluating integrals using horizontal instead of vertical bars (apparently something to do with Lebesque integration but thats way too complicated for me to understand). So I was thinking about this and it occurred to me that and inverse function flips a function that in a way taking its integral is taking the original integral but horizontally. This then lead me to come up with 2 identities I'm not sure are correct and I established graphically. $$ int_0^xf(x)dx=xf(x)-int_{f(0)}^{f(x)}f^{-1}(x)dx$$ or $$ int f(x)dx=xf(x)-int f^{-1}(f(x))df(x)$$ although I'm not sure if the second is valid notation but I think I've seen something like that written before somewhere. These are only valid in ranges where $f(x)$ is bijective. For example: $$be...