sin(2x-2分派）是怎么化成-cos2x
cos2x\u5982\u4f55\u53d8\u6210sin(2x+\u03c0/2)\uff1f\u5c31\u662f\u4e2a\u516c\u5f0f\u7b80\u5355\u5e94\u7528\u554a\uff0c\u7531\u516c\u5f0fsin\uff08a+\u03c0/2\uff09=cosa\u76f4\u63a5\u5f97\u5230\uff0c\u5c31\u5c06a\u6362\u62102x\u5c31\u53ef\u4ee5\u4e86\u3002
sin\uff082x-\u03c0/2\uff09
=sin\uff08-\u03c0/2+2x\uff09
=sin[-(\u03c0/2-2x)]
=-sin(\u03c0/2-2x)
=-cos2x
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