What is f(x) = int x-sin2x-6cosx dxf(x)=xsin2x6cosxdx if f(pi/2)=3 f(π2)=3?

1 Answer
Dec 22, 2016

f(x)=x^2/2+1/2cos2x-6sinx+7/2-pi^2/8f(x)=x22+12cos2x6sinx+72π28

Explanation:

f(x)=int(x-sin2x-6cosx)dxf(x)=(xsin2x6cosx)dx" "f(pi/2)=3 f(π2)=3

integrate term by term

f(x)=x^2/2+1/2cos2x-6sinx+Cf(x)=x22+12cos2x6sinx+C

f(pi/2)=1/2xx(pi/2)^2+1/2cos(2xxpi/2)-6sin(2xxpi/2)+C=3f(π2)=12×(π2)2+12cos(2×π2)6sin(2×π2)+C=3

pi^2/8+1/2cancel(cospi)^-1- 6cancel(sinpi)^0+C=3

pi^2/8-1/2+C=3

C=3+1/2-pi^2/8=7/2-pi^2/8

f(x)=x^2/2+1/2cos2x-6sinx+7/2-pi^2/8