定积分(x^3)/(1-x^2)^(1/2)dx 范围(0,1)

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定积分(x^3)/(1-x^2)^(1/2)dx范围(0,1)定积分(x^3)/(1-x^2)^(1/2)dx范围(0,1)定积分(x^3)/(1-x^2)^(1/2)dx范围(0,1).令x=cos

定积分(x^3)/(1-x^2)^(1/2)dx 范围(0,1)
定积分(x^3)/(1-x^2)^(1/2)dx 范围(0,1)

定积分(x^3)/(1-x^2)^(1/2)dx 范围(0,1)

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令x=cost 积分限变为从0到pi/2
原式=∫sint^3/cost*costdt=∫sint^3dt=2/3

注意 1-x^2≠0 x≠±1
是广义积分
原式=lim(b→1)∫(0 b)x^3/(1-x^2)^(1/2)dx
=-lim(b→1)∫(0 b)x^2d(1-x^2)^(1/2)
=-lim(b→1)x^2(1-x^2)^(1/2)|(b 0)+lim(b→1)∫(0 b)(1-x^2)^(1/2)dx^2
=-3/2lim(b→1)(1-x^2)^(3/2)|(b 0)
=3/2

令x=sin t 则dx=cos t dt
原式=∫[0,π/2]sint^3/cost*costdt=∫[0,π/2]sint^3dt=2/3