f cos 105 x +. x + cos y + cos2 = it, then it, then prove that: x2 + y2 +2+2 xyz = 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 cos^-1 x +cos^-1 y + cos ^-1 z=pi , prove that x^2+y^2+z^2+2xyz=1 .

If (i) cos^(-1) x + cos^(-1) y + cos^(-1) z = pi , prove that : x^(2) +y^(2) +z^(2) + 2xyz = 1 (ii) If sin^(-1) x + sin^(-1) y + sin^(-1) z = pi/2 , prove that : x^(2) +y^(2) +z^(2) +2xyz = 1

If cos^(-1) x +cos^(-1)y +cos^(-1)z =pi , then 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^-1x + cos^-1y+cos^-1z = pi then show 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 x cos A + y sin A = m and x sin A - y cos A = n, then prove that : x^(2) + y^(2) = m^(2) + n^(2)

If cos^(-1)x + cos^(-1)y - cos^(-1) z = 0 , then show that x^(2) + y^(2) + z^(2) - 2xyz = 1