化简sin(x+7π/4)+cos(x-3π/4）
题目
化简sin(x+7π/4)+cos(x-3π/4）
步骤我已经找到撒
sin(x+7π/4)+cos(x-3π/4)=sin(x+2π-π/4)+cos(x-π+π/4)我问下这一步是在干嘛?=sin(x-π/4)+cos[-(π-x-π/4)]=sin(x-π/4)+cos(π-x-π/4)=sin(x-π/4)-cos(x+π/4)=sin(x-π/4)-cos(x+π/2-π/4)=sin(x-π/4)-cos(π/2+x-π/4)=sin(x-π/4)+sin(x-π/4)=2sin(x-π/4)
sin(x+2π-π/4)+cos(x-π+π/4)我问下这一步是在干嘛?sin(x+2π-π/4为什么给以化成sin(x-π/4)
答案
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