sin163∘sin223∘+sin253∘sin313∘=（）_刷题宝

题干

sin163∘sin223∘+sin253∘sin313∘=（）

A： $- \frac{1}{2}$

B： $\frac{1}{2}$

C： $- \frac{\sqrt{3}}{2}$

D： $\frac{\sqrt{3}}{2}$

上一题下一题 0.0难度选择题更新时间:2016-05-23 05:41:58

答案(点此获取答案解析）

B

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