f(x)=sin2x-2sin²x 是怎么到下面这一步的?=sin2x-(1-cos2x)

f(x)=sin2x-2sin²x 是怎么到下面这一步的?=sin2x-(1-cos2x)
f(x)=sin2x-2sin²x 是怎么到下面这一步的?
=sin2x-(1-cos2x)

f(x)=sin2x-2sin²x 是怎么到下面这一步的?=sin2x-(1-cos2x)
cos2x=1-2(sinx)^2,则2(sinx)^2=1-cos2x
f(x)=sin2x-(1-cos2x)=sin2x+cos2x-1=√2sin(2x+π/4)-1