" 12.If "x^(2)+y^(2)+z^(2)=r^(2)" and "x,y,z>0," then "tan^(-1)((xy)/(zr))+tan^(-1)((yz)/(xr))+tan^(-1)((zx)/(yr))" is equal to "

If x^(2)+y^(2)+z^(2)=r^(2) and x,y,z>0, then tan^(-1)((xy)/(zr))+tan^(-1)((yz)/(xz))+tan^(-1)((zx)/(yr)) is equal to

If x^(2)+y^(2)+z^(2)=r^(2) , then Tan^(-1)((xy)/(zr))+Tan^(-1)((yz)/(xr))+Tan^(-1)((xz)/(yr))=

If x^(2)+y^(2)+z^(2)=r^(2), thentan ^(-1)((xy)/(zr))+tan^(-1)((yz)/(xr))+tan^(-1)((xz)/(yr)) is equal to pi(b)(pi)/(2)(c)0(d) none of these

If x^2+y^2+z^2=r^2,t h e ntan^(-1)((x y)/(z r))+tan^(-1)((y z)/(x r))+tan^(-1)((x z)/(y r)) is equal to pi (b) pi/2 (c) 0 (d) none of these

If x^2+y^2+z^2=r^2,t h e ntan^(-1)((x y)/(z r))+tan^(-1)((y z)/(x r))+tan^(-1)((x z)/(y r)) is equal to (a) pi (b) pi/2 (c) 0 (d) none of these

If x^2+y^2+z^2=r^2,t h e ntan^(-1)((x y)/(z r))+tan^(-1)((y z)/(x r))+tan^(-1)((x z)/(y r)) is equal to pi (b) pi/2 (c) 0 (d) none of these