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sin^4π/8-cos^4π/8=?
人气:319 ℃ 时间:2020-06-13 15:16:00
解答
sin^4π/8-cos^4π/8=
=(sin^2π/8-cos^2π/8)(sin^2π/8+cos^2π/8)
=sin^2π/8-cos^2π/8
=-cosπ/4
=-√2/2
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