sin420 · cos330 + sin(-690)·cos(-660)
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sin420 · cos330 + sin(-690)·cos(-660)
![sin420 · cos330 + sin(-690)·cos(-660)](/uploads/image/z/19931336-8-6.jpg?t=sin420+%C2%B7+cos330+%2B+sin%EF%BC%88-690%EF%BC%89%C2%B7cos%EF%BC%88-660%EF%BC%89)
sin420cos330+sin(-690)cos(-660)
=sin60cos30+sin30cos60
=sin(30+60)
=1
=sin60cos30+sin30cos60
=sin(30+60)
=1
化简:sin420°乘cos750°+sin(-330°)乘cos(-660°)乘tan(225°)
化简:tan45°+sin420°×1/tan(-60°)+1/2(sin平方15°+cos平方15°)
cos330°等于 cos(360°-30°),应该用诱导公式几呢
计算:(1)sin420度cos750度+sin(-330度)cos(-660度) (2)tan675度+tan765度
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