若f（sinx）=3-cos2x,则f（cos15度）=
问题描述：
若f（sinx）=3-cos2x,则f（cos15度）=
答
cos15°=sin(90°-15°)=sin75°
所以f(cos15°)
=f(sin75°)
=3-cos(2×75°)
=3-cos150°
=3-(-√3/2)
=3+√3/2