首先化简f(x)=sinx的4次方+cosx的2次方,f(x)=(sinx)^4+(cosx)^2=[(sinx)^2]^2+1-(sinx)^2=[(sinx)^2-1/2]^2+3/4=1/4[2*(sinx)^2-1]^2+3/4 =1/4(cos2x)^2+3/4=1/4(cos2x)^2-1/8+1/8+3/4=1/8cos4x+7/8cos4x的区间,[-1,...