1.y=sinccos30°-cosxsin30°)cosx
=sinx·cosx·cos30°-cos²x·sin30°
=(1/2)[sin2xcos30°-(1+cos2x)sin30°]
=(1/2)(sin2xcos30°-cos2xsin30° -1/2)
=(1/2)sin(2x-30°) -1/4,
最小值为 -1/2 -1/4=-3/4
2.a=√2[(√2/2)sin14°+(√2/2)cos14°]
=√2(sin14°cos45°+cos14°sin45°)
=√2·sin59°,
同理,b=sin16°+cos16°=√2·sin61°
而 c=√6/2=√2·sin60°,
则sin59°