(1+sina+cosa)[sin(a/2)-cos(a/2)]/√(2+2cosa) =(2sina/2*cosa/2+2cos^2a/2)[sin(a/2)-cos(a/2)]/√(2+4cos^2a/2-2)=2cosa/2(sina/2+cosa/2)[sin(a/2)-cos(a/2)]/√(4cos^2a/2)=-2cosa/2*cosa/2cosa/2=-cosa