Question

Which theorem or postuate can be used to prove two triangles are similar? thanks in advance

Answer 1

There are two theorems/postulates that we can use; SAS and ASA. These two work because they have properties that force the triangles to retain their shape; no resizing of any sort could be done to them.

See the attached images below to see an example of these triangles. The left one is ASA and the right on is SAS.

:)