化简 sin(x-20°)+cos(x+70°)+sin(x+20°)sec(70°-x)麻烦稍微写下过程呐.
问题描述：
化简 sin(x-20°)+cos(x+70°)+sin(x+20°)sec(70°-x)
麻烦稍微写下过程呐.
答
sin(x-20)=sin(110-x)
cos(x+70)=-cos(110-x)
sin(x+20)=cos(70-x)
sec(70-x)=1/cos(70-x)
原式=sin(110-x))-cos(110-x)+cos(70-x)*1/cos(70-x)=2^0.5sin(65-x)+1