Michael J. answered 07/12/17
Tutor
5
(5)
Effective High School STEM Tutor & CUNY Math Peer Leader
Find the distance between point P and point Q.
" " distance between point Q and point R.
" " distance between point R and point S.
" " distance between point S and point P.
Then add those distances to get the perimeter. It is a square if the 4 distances are the same, and each pair of lines are perpendicular to each other. Perpendicular means the intersecting lines have negative reciprocal slopes.