sinθ=12/13,则cos^4θ-sin^4θ

ff12345672022-10-04 11:39:541条回答

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焰蓝冰 共回答了19个问题 | 采纳率89.5%
∵sinθ=12/13
∴cosθ=±5/13
cos^4θ-sin^4θ
=(cos^2θ + sin^2θ)(cos^2θ - sin^2θ)
=cos^2θ - sin^2θ
=25/169 - 144/169
= -119/169
1年前

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