i want to find angle between two 3d dots in kinect skeleton

if i want to find angle of btween kneejoint and hipjoint, how can i do? just i knew only x,y,z values of joints... somebody help me plz..

[NURUL AMIRA MHD RIZAL]

How do you know value of the joints?

Answer 1

[Youssef Khmou]

try to verify these relations :

 r=sqrt(x^2+y^2+z^2);

 phi=acos(z/r); % radian
 theta=acos(x/(r*cos(phi)); radian