The hinge theorem says that if two triangles 
and 
have congruent sides 
and 
and 
, then 
.
Hinge Theorem
This entry contributed by Floor van Lamoen
Explore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W., with contributions by Floor van Lamoen. "Hinge Theorem." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/HingeTheorem.html