#f(x)=e^(8x)+cos(x)sin(x)#
#d /(d x) f(x)=8*e^(7x)*l n e-sin x*sin x +cos x *cos x#
#d /(d x) f(x)=8*e^(7x)*l n e-sin^2 x+cos^2 x#
#cos^2 x=1-sin^2 x#
#d /(d x) f(x)=8*e^(7x)*l n e-sin^2 x+(1-sin^2 x)#
#d /(d x) f(x)=8*e^(7x)*l n e-sin^2 x+1-sin^2 x#
#d /(d x) f(x)=8*e^(7x)*l n e+1-2sin^2 x#