sin14·cos16·+sin76·cos74·=?

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sin14·cos16·+sin76·cos74·=?

是sin14°cos16°+sin76°cos74°吧?
=sin14°cos16°+cos14°sin16°
=sin(14°+16°)
=sin30°
=1/2

sin14·cos16·+sin16·cos14
=sin(14+16)
=sin30
=1/2