若cos2X/sin(X—45度)=根号2/2 则cosX+sinX?

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若cos2X/sin(X—45度)=根号2/2 则cosX+sinX?

若cos2X/sin(X—45度)=根号2/2 则cosX+sinX?
若cos2X/sin(X—45度)=根号2/2 则cosX+sinX?

若cos2X/sin(X—45度)=根号2/2 则cosX+sinX?
答案是1/2 cos2X可以分解成(cosX+sinX)(cosX-sinX),分母可以化成 根2/2乘以(sinX-cosX) 追问:分母可以化成 根2/2乘以(sinX-cosX)?是如何化的?回答:sin(X-45°)=sin(X-π/4)=sinXcosπ/4-cosXsinπ/4=根2/2(sinX-cosX)