what does SAS mean?

For those interested, here's a proof by Euclid:

http://aleph0.clarku.edu/~djoyce/java/elements/bookI/propI4.html

It is a reason of proving two triangles that they are congruent.

It means they have the same sides and a same angle which is between the two sides.

For this two triangles, since PN=SQ , MP=RS , angleP=angleS

So these triangles are congruent , with the reason SAS

it means side angle side and it applies to right triangles.

That was a  great answer problem.  And thanks for the reference Chris.