1.sin²40°+sin²50°等于多少 - 知识问答

1.sin²40°+sin²50°等于多少

4个回答

1.sin²40°+sin²50°
sin²40°+sin²50°
=sin²40°+cos²(90°-50°)
=sin²40°+cos²40°
=1
2.如何证明sin（30°+α）=cos（60°-α）
sin(30°+α)
=cos[90°-(30°+α)]
=cos(60°-α)

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