I have seen a proof of SAS congruence rule using rigid transformations. So, why isn't it a theorem. Also, are there any other proofs of it using the existing postulates? I am very confused regarding this matter.
I was able to prove that if two triangles two corresponding sides and the angle contained by those sides equal, then the triangles are congruent, using the postulates that describe parallel lines and some construction. So, does that make it a theorem? I highly doubt that I used any other assumptions or followed any incorrect steps.
Please clear my above confusion.