∫(cosx)^5dx =∫(cosx)^4*cosxdx ==∫(cosx)^4*dsinx =∫[(cosx)^2]^2*dsinx ==∫[1-(sinx)^2]^2*dsinx =∫[1-2(sinx)^2+(sinx)^4]*dsinx ==sinx-(2/3)(sinx)^3+(1/5)(sinx)^5+C.
d[cos(x^5)]/dx=-5x^4*sin(x^5)
