cos33°cos87°+sin33°cos177°

2024-11-26 09:15:07
cos33°cos87°+sin33°cos177°希望能解答下
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cos177°=cos(90°+87°) =-cos87°所以, 原式=cos33°cos87°-sin33°sin87° =cos(33°+87°) =cos120° =-2分之1

2024-11-26 09:15:07
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