已知sin(a-60°)=1/2sina,且0°
人气：469 ℃ 时间：2020-09-20 15:38:41
解答
因为 sin(a-60°)=sinacos60°-cosasin60°=1/2sina-(根号3)/2cosa=1/2sina
所以cosa=0
又因为0
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