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cosa=3/5,0
人气:177 ℃ 时间:2020-04-16 20:07:47
解答
cosa=3/5
0所以sina>0
(sina)^2+(cosa)^2=1
sina=√[1-(cosa)^2]=4/5
cos(a-π/6)
=cosacosπ/6+sinasinπ/6
=(3/5)*(√3/2)+(4/5)(1/2)
=(3√3+4)/10
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