求∫x²/(x²+1)²dx
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∫x^2/(x^2+1)^2dx
let
x=tanu
dx=(secu)^2 du
∫[x^2/(x^2+1)^2 ]dx
=∫[ (tanu)^2/(secu)^4 ] [(secu)^2 du]
=∫[ (tanu)^2/(secu)^2 ] du
=∫ (sinu)^2 du
=(1/2)∫ ( 1- cos2u) du
=(1/2)( u- (1/2)sin2u) +C
=(1/2)[ arctanx - x/(x^2+1) ] +C
let
x=tanu
dx=(secu)^2 du
∫[x^2/(x^2+1)^2 ]dx
=∫[ (tanu)^2/(secu)^4 ] [(secu)^2 du]
=∫[ (tanu)^2/(secu)^2 ] du
=∫ (sinu)^2 du
=(1/2)∫ ( 1- cos2u) du
=(1/2)( u- (1/2)sin2u) +C
=(1/2)[ arctanx - x/(x^2+1) ] +C
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