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COS（195度）的三角函数值怎么求？（要详细过程）
解答：
cos195°
=cos(180°+15°)
=-cos15°
=-cos(45°-30°)
=-(cos45°cos30°+sin45°sin30°)
=-[(√2/2)*(√3/2)+(√2/2)*(1/2)]
=-(√6+√2)/4
解答：
cos195°
=cos(180°+15°)
=-cos15°
=-cos(45°-30°)
=-(cos45°cos30°+sin45°sin30°)
=-[(√2/2)*(√3/2)+(√2/2)*(1/2)]
=-(√6+√2)/4