y=sin^4x-cos^4x的最小正周期是
问题描述：
y=sin^4x-cos^4x的最小正周期是
答
y=sin^4x-cos^4x=-(cos^2x-sin^2x)(cos^2x+sin^2x)=-(cos^2x-sin^x)=-cos2x
T=∏