已知tana=cosa,那么sina等于
人气：147 ℃ 时间：2020-04-09 20:56:46
解答
tana = cosa
sina/cosa = cosa
sina = cos²a
sina = 1 - sin²a
sin²a + sina - 1 = 0
sina = (√5 - 1)/2 ( sina = (-1- √5)/2 < -1舍去 )
综上：sina = (√5 - 1)/2
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