The length of the side is the distance between the two points. The distance between two points is:
d^2=(x2-x1)^2+(y2-y1)^2, so in this case:
d^2=(-3-3)^2+(2-2)^2
d^2=(-6)^2+0^2
d^2=36
d=√36
d=6 units.
Note we could have just observed that the y-coordinate did not change and know that the distance between the two points or the length of the sides was just the change in x: 3--3=6 units.
