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sin²1°+sin²2°+sin²3°+.+sin²89°= -1
为什么?
人气:384 ℃ 时间:2020-09-18 19:16:59
解答
sin²1°+sin²2°+sin²3°+.+sin²89°
=sin²1°+cos²1°+sin²2°+cos²2°+----+sin²45°
=44+1/2
=89/2
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