" 11.Prove that "(cos(pi+theta)cos(-theta))/(cos(pi-theta)cos((pi)/(2)+theta))=-cot theta

Prove that : (cos(pi+theta)cos(-theta))/(sin (pi-theta) cos (pi/2+ theta))= cot^2 theta.

Prove that: 2cos theta cos((pi)/(3)+theta)cos((pi)/(3)-theta)=cos3 theta

Prove that cos theta + cos ((2pi)/(3)- theta)+ cos ((2pi)/(3)+ theta)=0

Prove that: (cos(2 pi+theta)csc(2 pi+theta)tan(pi/2+theta))/(sec(pi/2+theta)cos theta cot(pi+theta))=1

Prove that cos theta +cos ((2pi)/(3)-theta)+cos ((2pi)/(3)+theta)=0

Prove that (sin(3pi-theta)cos(theta- pi/2)tan((3pi)/(2)-theta))/(cosec((13pi)/(2)+theta)sec(3pi+theta)cot(theta- pi/2))=cos^(4)theta

Prove that: 4\ costhetacos\ (pi/3+theta)cos(pi/3-theta)=cos3theta

cos((3 pi)/(2)+theta)*cos(2 pi+theta)=

Prove that (cos (pi-theta).cot(pi/2 +theta).cos(-theta))/(tan(pi+theta).tan((3pi)/(2)+theta).sin(2pi-theta))=cos theta