Denote the spherical distance $d(A,B)$ of two points $A,B$ on some unit sphere surface is the shortest distance of path from A to B on the surface.
Given length of three sides $a,b,c$. Ask what's the sufficient and necessary condition for $a,b,c$ such that there exists three point $A,B,C$ on the unit sphere surface and $d(A,B)=a,d(B,C)=b,d(C,A)=c$.