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If `intsin^(5)x cos^(4)x dx =A cos^(9) x +B cos^(7)x+C cos^(5)x+D`,then 9A +7B +5C=A. 1B. 0C. `-1`D. none of these |
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Answer» Correct Answer - b `I=intsin^(5)xcos^(4)x dx` `rArr I=intsin^(4)x cos^(4)x sinx dx` `rArr I=- int (1-cos^(2)x)^(2)cos^(4) xd (cosx)` `rArrI=- int(1-t^(2))^(2)t^(4)dt` , where t cos x `rArrI=-int(t^(4)-2t^(6)+t^(8))dt` `rArrI=-(t^(9))/(9)+(2)/(7)t^(7)-(1)/(5)t^(5)+D` `rArrI=-(1)/(9)cos^(9)x+(2)/(7)cos^(7)x-(1)/(5)cos^(5)x+D` `:. A=-(1)/(9),B =(2)/(7)andC=-(1)/(5)rArr9A+7B+5C=0` |
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