cosπ\9·cos2π\9·cos3π\9·cos4π\9 等于多少?

发布时间:2021-03-10 02:31:09

cosπ\9·cos2π\9·cos3π\9·cos4π\9 等于多少?

网友回答

cosπ/9·cos2π/9·cos3π/9·cos4π/9 =(2sinπ/9cosπ/9·cos2π/9·cosπ/3·cos4π/9)/(2sinπ/9)=(2sin2π/9·cos2π/9·(1/2)·cos4π/9)/(4sinπ/9)=((1/2)2sin4π/9·cos4π/9)/(8sinπ/9)=((1/2)sin8π/9)...
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