I'm having a little trouble with a question I'm doing. I'll write it below.
The vertices of a quadrilateral are C(-2,4), D(3,9), E(6,6), and F(1,1).
a) Show that the quadrilateral is a rectangle.
First I calculated the length of its four sides.
CD = square root of 50
DE = square root of 18
EF = square root of 50
CF = square root of 18
Ok, so far so good. Now I have to show that it has a right angle, which would require two adjacent sides being perpendicular.
mCD = 1, but mDE = -6/0?
Did I mess up somewhere? Any help/advice is appreciated.