sina-cosa=1/2.cos2a=?
sina-cosa=1/2.cos2a=?
数学人气:521 ℃时间:2020-04-15 18:26:43
优质解答
因为sina-cosa=1/2.所以(sina-cosa)²=1-2sinacosa=1/4所以2sinacosa=3/4(sina+cosa)²=1+3/4=7/4所以sina+cosa=√7/2(sina+cosa)(sina-cosa)=sina²-cosa²=√7/4cos2a=cosa²-sina²=-√...
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