证明cos²x-cos²y=sin²(x-y)-2sinxcosysin(x-y).万分感激!
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![证明cos²x-cos²y=sin²(x-y)-2sinxcosysin(x-y).万分感激!](/uploads/image/z/7083667-19-7.jpg?t=%E8%AF%81%E6%98%8Ecos%26%23178%3Bx-cos%26%23178%3By%3Dsin%26%23178%3B%28x-y%29-2sinxcosysin%28x-y%29.%E4%B8%87%E5%88%86%E6%84%9F%E6%BF%80%21)
证明cos²x-cos²y=sin²(x-y)-2sinxcosysin(x-y).万分感激!
证明cos²x-cos²y=sin²(x-y)-2sinxcosysin(x-y).万分感激!
证明cos²x-cos²y=sin²(x-y)-2sinxcosysin(x-y).万分感激!
反过来证明 从后面往前面证.
你的题目打错了吧 !