1.

`int_(0)^(1)(x tan^(-1)x)/((1+x^(2))^(3//2))dx` का मान ज्ञात कीजिए ।

Answer» `int_(0)^(1)(xtan^(-1)x)/((1+x^(2))^(3//2))dx`
यदि `tan theta= x rArr sec^(2)theta d theta = dx` तथा सीमायें हैं।
`theta=0` पर `x=0` व `theta=pi//4` पर `x = 1,` तब
`int_(0)^(1)(x tan^(-1))/((1+x^(2))^(3//2))dx=int_(0)^(pi//4)(theta tan theta)/(sec^(3)theta).sec^(2) theta d theta`
`=int_(0)^(pi//4)theta sin theta d theta`
खण्डशः समाकलन करने पर ,
`=[-theta cos theta]_(0)^(pi//4)-int_(0)^(pi//4)(-cos theta) d theta`
`=[-theta-cos theta]_(0)^(pi//4)+[sinx theta]_(0)^(pi//4)`
`=-(pi)/(4)cos.(pi)/(4)+sin.(pi)/(4)`
`=((-pi)/(4sqrt2)+(1)/(sqrt2))=((4-pi))/(4sqrt2)=(sqrt2(4-pi))/(8)`


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