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मूल्यांकन कीजिएः `int_(0)^(pi//2) cos^(3)xdx` |
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Answer» `underset(0)overset(pi//2)int cos^(3)xdx` `=underset(0)overset(pi//2)int ((cos 3x+3cosx)/(4))dx [therefore cos 3x=4cos^(3)x-3cosx]` `=1/4 underset(0)overset(pi//2)int (cos 3x+3cos x)dx` `=1/4 [(sin 3x)/(3)+ sin x]_(0)^(pi//2)` `=1/4[{1/3sin((3pi)/(2))+3 sin((pi)/(2))}-{(sin 0)/(3)+3 sin 0}]` `=1/4 [{1/3 xx (-1)+3}-(0+0)]` `=1/4(-1/3+3)=1/4xx8/3=2/3` |
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