If `x +y+z = 180^@`, then `cos2x + cos2y-cos2z` is equal to

26. If x,y,z are in A.P,then (sin x-sin z)/(cos z-cos x) is equal to a.tan y b.cot y c.sin y d.cos y

If x,y,z are in A.P, then ( sin x - sin z)/( cos z - cos x) is equal to

If x + y = z then cos ^ (2) x + cos ^ (2) y + cos ^ (2) z-2cos x cos y cos z =

If sin x + sin y + sin z = 0 and cos x + cos y + cos z = 0 then prove that cot (x+y)/2 = cot z and cos (x-y)/2 = pm 1/2

If x+y=z then cos^(2)x+cos^(2)y+cos^(2)z-2cos x cos y cos z is equal to