11. If cos- 'x + cos-1 y + cos- | z = L, then prove V that x + y + 2 + 2xyz = 1.

If cos^(-1) x + cos^(-1) y + cos^(-1) z = pi , then

If cos^-1 x +cos^-1 y + cos ^-1 z=pi , prove that x^2+y^2+z^2+2xyz=1 .

If cos^(-1) x + cos^(-1) y + cos^(-1) z = pi , prove that x^(2) + y^(2) + z^(2) + 2xyz = 1

If cos^(-1) x + cos^(-1) y + cos^(-1) z = pi , prove that x^(2) + y^(2) + z^(2) + 2xyz = 1

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 cos^-1 x+cos^-1 y+cos^-1 z=pi and x+y+z= 3/2, then prove that x=y=z

If cos^-1 x+cos^-1 y+cos^-1 z=pi and x+y+z= 3/2, then prove that x=y=z

If cos^(-1)x+cos^(-1)y+cos^(-1)z=pi , then

If cos^(-1)x+cos^(-1)y+cos^(-1)z=pi , then

If cos^(-1)x+cos^(-1)y+cos^(-1)z=pi , then