化简sin(5/6π-α)+sin(5/6π+α)
问题描述：
化简sin(5/6π-α)+sin(5/6π+α)
答
sinθ+sinφ=2sin[(θ+φ)/2]cos[(θ-φ)/2]
sin(5/6π-α)+sin(5/6π+α)
=2sin(5/6π)cosα
=2sin(π-1/6π)cosα
=2×0.5cosα
=cosα