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cos(7π/2-α)等于-sinα吗
人气:359 ℃ 时间:2020-04-06 18:21:21
解答
等于,cos(7π/2-α)
=cos(4π-π/2-α)
=cos[4π-(π/2+α)]
=cos(π/2+α)
=-sinα
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