Question

Sin(35pi/2 - a)+cos(68pi-a)

Answer 1

$sin(frac{35pi}{2}-a)-cos(68pi -a)=\\=sin(8cdot 2pi +frac{3pi}{2}-a)+cos(34cdot 2pi -a)=\\=sin(frac{3pi}{2}-a)+cos(-a)=-cosa+cosa=0$