con²(5π/12)-sin²(7π/12)=cos²(5π/12)-sin²

东方文英2022-10-04 11:39:541条回答

con²(5π/12)-sin²(7π/12)=cos²(5π/12)-sin²(π-7π/12)=cos²(5π/12)-sin²(5π/12)=cos(2*5π/12)=cos(5π/6)=-(√3)/2
cos²(5π/12)-sin²(5π/12)=cos(2*5π/12)怎么变过来的

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hongcanyuan 共回答了18个问题 | 采纳率77.8%
cos²(5π/12)-sin²(5π/12)=cos(2*5π/12)
二倍角公式:
cos2α=(cosα)^2-(sinα)^2
1年前

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