1.

दिया गया है कि `a_(n)=int(sin^(2){(n+1)x})/(sin2x)dx` `int_(0)^(4pi)|cosx|dx` किसके बराबर है ?

Answer» Correct Answer - D
माना `I=int_(0)^(4pi)|cosx|dx`
`=2int_(0)^(2pi)|cosx|dx`
`[becauseint_(0)^(2a)f(x)dx=2int_(0)^(a)f(x)dx"यदि"f(2a-x)=f(x),"यहाँ",|cos(4pi-x)|=|cosx|]`
`=2*2int_(0)^(pi)|cosx|dx`
`[because|cos(2pi-x)|=|cosx|]`
`=2*2*2int_(0)^(pi//2)|cosx|dx`
`[because|cos(pi-x)|=|-cosx|=|cosx|]`
`=8int_(0)^(pi//2)cosxdx`
`[becausecosxgt0,AAx in(0,(pi)/(2))]`
`=8[sinx]_(0)^(pi//2)=8["sin"(pi)/(2)-sin0]=8`


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