1.

Evaluate:`(sin^3x dx)/((cos^4x+3cos^2x+1)tan^(-1)(secx+cosx)`A. `tan^(-1)(secx+cosx)+C`B. `log_(e)|tan^(-1)(secx+cosx)|+C`C. `(1)/((secx+cosx)^(2))+C`D. none of these

Answer» Correct Answer - b
Let `I=int(sin^(3)x)/((cos^(4)x+3cos^(2)x+1)tan^(-1)(secx+cosx))dx`
`rArrI=int((sin^(3)x)/(cos^(2)x))/((cos^(2)x+3+sec^(2)x)tan^(-1)(secx+cosx))dx`
`I=int(1)/(1+(secx+cosx)^(2))xx(sinx(1-cos^(2)x))/(cos^(2)x)xx(1)/(tan^(-1)(secx+cosx))dx`
`rArrI=int(1)/(tan^(-1)(secx+cosx))xx(1)/(1+(secx+cosx)^(2))xx(tanxsec x-sinx)dx`
`rArrI=int(1)/(tan^(-1)(secx+cosx))d{tan^(-1)(secx+cosx)}`
`rArrI=log|tan^(-1)(secx+cosx)|+C`


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