1.

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

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`


Discussion

No Comment Found

Related InterviewSolutions