求值：sin21°cos81°-sin69°cos9°=______．

来源：学生作业帮编辑：神马作文网作业帮分类：综合作业时间：2024/11/13 23:55:03

sin21°cos81°-sin69°cos9°=sin21°cos（90°-9°）-sin（90°-21°）cos9°
=sin21°sin9°-cos21°cos9°=-（cos21°cos9°-sin21°sin9°）=-cos（21°+9°）=-cos30°=-

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故答案为：-

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求值:(sin9°+sin6°cos15°)/(cos9°-sin6°sin15°) 计算：sin21°+sin22°+sin23°+…+sin288°+sin289°+sin290°= ___ ．化简COS8°-SIN17°SIN9°/COS9° 计算：sin21°+sin22°+sin23°+…+sin287°+sin288°+sin289°． 1.比大小：tan21°和tan31°；2.sin21°和cos21°；3.cos21°和cos22° 化简（sin15°cos9°-cos66°）/（sin15°sin9°+sin66°）的结果是? 求值：cos2α+cos2（α+120°）+cos2（α+240°）的值为 ______．求值：cos20°sin20° 3.76°=______度 ______分 ______秒．求值：cos40°(1+3tan10°) tan36°tan72°求值要过程 27.24°=______度______分______秒，108°21′36″=______度．