y=cos2x+sinx(-π/6
问题描述：
y=cos2x+sinx(-π/6
答
y=cos2x+sinx=1-2(sinx)^2+sinx
-π/6 y=cos^2 x +sinx 为什么等于1-2sinx^2+sinxcos2x = cosx^2 - sinx^2 = 1 - sinx^2 - sinx^2 = 1-2(sinx)^2cosx^2 - sinx^2这是什么？三角函数和差化积 cos(x + y) = cosx*cosy - sinx* siny此题中x = y.