notice the point R
is a vertex between two "vertical angles" [tex]\measuredangle SRT\ and\ \measuredangle QRP[/tex]
those two folks are also the same
so now, we have the left triangle has angle P equals to angle T on the other triangle
we also have the side on the left triangle of PR equals the side of TR on the other triangle, and those two verticals angles are equal to each other
does ASA ring a bell?
