If `theta` lies in the first quadrant and `costheta=8/(17)` , then prove that `cos(pi/6+theta)+cos(pi/4-theta)+cos((2pi)/3-theta)=((sqrt(3)-1)/2+1/(sqrt(2)))(23)/(17)`

If theta lies in the 1st quadrant and costheta=8/(17) then prove that cos(pi/6+theta)+cos(pi/4-theta)+cos((2pi)/3-theta)=((sqrt(3)-1)/(2)+1/sqrt2) cdot(23)/17 .

If theta lies in the first quadrant and cos theta=(8)/(17), then prove that cos((pi)/(6)+theta)+cos((pi)/(4)-theta)+cos((2 pi)/(3)-theta)=((sqrt(3)-1)/(2)+(1)/(sqrt(2)))(23)/(17)

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

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

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

If theta lies in the first quadrant and costheta=(8)/(17) , then find the value of cos(30^(@)+theta)+cos(45^(@)-theta)+cos(120^(@)-theta) .

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

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

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

If theta = pi/7 prove that cos theta* cos 2theta * cos 3theta = 1/8