f（x）=(1+cotx)sinx^2-2sin(x+π/4)sin(x-π/4) =（1+cosx/sinx)*sinx ^2-(sinx ^2-cosx ^2)=cosx ^2+sinxcosx1、若tana=2,1/(cosa ^2)=seca ^2=1+2*2=5f(a)=cosa ^2+sinacosa=cosa ^2(1+tana)=1/5*(1+2)=3/52、f（...