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

If x, y, z are all non zero and x^(2)+y^(2)+z^(2)=r^(2) then tan ^(-1)((y z)/(x r))+tan ^(-1)((z x)/(y r))+tan ^(-1)((x y)/(z r))

If tan ^(-1) x+tan ^(-1) y+tan ^(-1) z=(pi)/(2), then 1-x y-y z-z x=

If tan ^(-1) x+tan ^(-1) y+tan ^(-1) z=(pi)/(2) then x y+y z+z x=

If x,y,z are in A.P. and tan^(-1)x , tan^(-1)y and tan^(-1) z are also in A.P., then :

If x,y,z are in A.P. and tan^(-1) x , tan^(-1) y and tan^(-1) z are also in A.P. then :

If z^(2)+z+1=0 then sum_(r=1)^(6)(z^(r)+(1)/(z^(r)))^(2)=

Lines (x-2)/(1)=(y-3)/(1)=(z-4)/(-K) and (x-1)/(K)=(y-4)/(2)=(z-5)/(1) are coplanar if

If y = a^(1/(1-log_(a) x)) and z = a^(1/(1-log_(a)y))",then prove that "x=a^(1/(1-log_(a)z))