计算:sin²10°+sin²20°+sin²30°+……sin²80°=
来源:学生作业帮 编辑:拍题作业网作业帮 分类:数学作业 时间:2024/05/22 11:55:24
计算:sin²10°+sin²20°+sin²30°+……sin²80°=
=sin²10°+sin²20°+sin²30°+sin²40°+cos²40°+cos²30°+cos²20°+cos²10°
=sin²10°+cos²10°+sin²20°+cos²20°+sin²30°+cos²30°+sin²40°+cos²40°
=(sin²10°+cos²10°)+(sin²20°+cos²20°)+(sin²30°+cos²30°)+(sin²40°+cos²40°)
=1+1+1+1
=4
=sin²10°+cos²10°+sin²20°+cos²20°+sin²30°+cos²30°+sin²40°+cos²40°
=(sin²10°+cos²10°)+(sin²20°+cos²20°)+(sin²30°+cos²30°)+(sin²40°+cos²40°)
=1+1+1+1
=4
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sin²1°+sin²2°+sin²89°+sin²88°=
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