Question

cos(7pi/4)-sin(5pi/4) как решать?

Answer 1

$cosfrac{7pi }{4}-sinfrac{5pi }{4}=cos(2pi -frac{pi}{4})-sin(pi +frac{pi}{4})=\\=cosfrac{pi}{4}+sinfrac{pi}{4}=frac{sqrt2}{2}+frac{sqrt2}{2}=sqrt2$