sin(x/2 + π/6)=1 cos(2π/3 -x)=?
问题描述：
sin(x/2 + π/6)=1 cos(2π/3 -x)=?
答
sin(x/2 + π/6)=1
x/2 + π/6=π/2+2kπ
x/2=π/3+2kπ
x=2π/3+4kπ
x-2π/3=4kπ
cos(2π/3-x)=cos(x-2π/3)=1
答
cos(2π/3 -x)
=-cos[π-(2π/3-x)]
=-cos(x+π/3)
=-[1-2sin²(x/2+π/6)]
=-(1-2)
=1
答
sin(x/2 + π/6)=1
则
cos( π/3 - x/2)=cos( π/2 - (x/2 + π/6) )=sin(x/2 + π/6)=1
cos(2π/3 -x)
=2cos²( π/3 - x/2)-1
=2-1
=1