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sin10分之π×cos5分之π
人气:182 ℃ 时间:2020-09-10 18:51:35
解答
原式=2sinπ/10cosπ/10cosπ/5/(2cosπ/10)
=sinπ/5cosπ/5/[2sin(π/2-π/10)]
=sin2π/5/(4sin2π/5)
=1/4
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