1/2 (x+x cos (2 x)=cos (x)+1=cos (2 x) x cos^2 (x)=2 cos^2 (x/2)=2 sin (pi/4-x) sin (x+pi/4) x/2-1/2 x sin^2 (x)+1/2 x cos^2 (x)=cos (x)+1=cos^2 (x) -sin^2 (x)