If `cos^(-1)x+cos^(-1)y+cos^(-1)z=pi,t h e n prove t h a t` `x^2+y^2+z^2+2x y z=1`

Explanation

`cos^-1x+cos^-1y+cos^-1z = pi`

`=>pi/2-sin^-1x+pi/2-sin^-1y+pi/2-sin^-1z = pi`

`=>sin^-1x+sin^-1y+sin^-1z = pi/2`

`=>2(sin^-1x+sin^-1y+sin^-1z) = pi`

`=>2(sin^-1x+sin^-1y+sin^-1z) = cos^-1x+cos^-1y+cos^-1z`

So, option -`b` is correct.

Now,

`cos^-1x+cos^-1y+cos^-1z = pi`

...