The Isosceles Triangle Theorem Suppose that ABC is an htriangle. (1) If d(A,B) = d(A,C) then <ABC = <ACB. (2) If <ABC = <ACB then d(A,B) = d(A,C).


Proof Consider the htriangles ABC and ACB. The order of vertices is significant, so we use different colours!
(1) We have
(2)


return to congruence page 