cos^2x/sin( π/4+x)cos(x+π/4),求① f(5π/12)
问题描述：
cos^2x/sin( π/4+x)cos(x+π/4),求① f(5π/12)
答
f(x)=cos^2x/sin( π/4+x)cos(x+π/4),
f(5π/12)=cos²(5π/6)/[(sin2π/3)cos(2π/3)]
=(3/4)/(-√3/2*1/2)
=-√3