cos36'cos99'-sin36'sin99'等于多少

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原式＝cos(36'+99')＝cos135'＝－√2/知拿2

**楼上的是来捣乱的？搭蠢搭档斗**

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cos36'雀拍烂cos99'-sin36'sin99'顷漏
=cos36'cos99'-cos36'cos99'贺羡
=0

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