sin(π/4-3x)cos(π/3-3x)- sin(π/4+3x)sin(π/3-3x)=
问题描述:
sin(π/4-3x)cos(π/3-3x)- sin(π/4+3x)sin(π/3-3x)=
答
sin(π/4-3x)=sin[π/2-(π/4+3x)]
=cos(π/4+3x)
sin(π/4-3x)cos(π/3-3x)- sin(π/4+3x)sin(π/3-3x)
=cos(π/4+3x)cos(π/3-3x)- sin(π/4+3x)sin(π/3-3x)
=cos(π/4+3x+π/3-3x)=cos(π/4+π/3)
=√2/2*1/2-√2/2*√3/2
=(√2-√6)/4