This is my first post and I wish to get help in finding an analytically way to get the coordinate of an irregular tetrahedron. let ABCD be the 4 vertices of the tetrahedron in 3D, all vertices have different (x,y,z). the coordinate of vertex D is known (Xd,Yd,Zd), and the 3 angle between faces at vertex D are also known angle adb , adc, cdb. Coordinate of the other 3 vertices A, B, C are known on X, Y but not on Z. (ie Za,Zb,Zc are unknown). As I can expect this system will give me 2 solutions +&-. I've started by developing system of equation for the sides using cosines and as a function of Za,Zb,Zc, where (Zb-Za)^2= [Lda^2+Ldb^2-2Lda*Ldb*cos(adb)]-[(xb-xa)^2+(Yb-Ya)^2] Any suggestions on how to approach this problem would be appreciated.