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Question Number 29454 by prof Abdo imad last updated on 08/Feb/18
f is a function increasing and C^1 on [a,b] prove   ∫_(f(a)) ^(f(b))  f^(−1) (t)dt = ∫_a ^b  x f^′ (x)dx
fisafunctionincreasingandC1on[a,b]provef(a)f(b)f1(t)dt=abxf(x)dx
Commented by prof Abdo imad last updated on 27/Feb/18
let put f^(−1) (t)=x ⇒t=f(x)⇒dt =f^′ (x)dx  ∫_(f(a)) ^(f(b))  f^(−1) (t)dt= ∫_a ^(b )  x f^′ (x)dx .
letputf1(t)=xt=f(x)dt=f(x)dxf(a)f(b)f1(t)dt=abxf(x)dx.

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