cos(2π-a)=cos(-a)=cosa=24/25
a在第四象限
所以sina
若cos(2pi-a)=24/25,且(3/2)pi
若cos(2pi-a)=24/25,且(3/2)pi
数学人气:948 ℃时间:2020-04-19 10:19:08
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