Lydia is trying to prove that a quadrilateral in a coordinate plane is a square. First, she uses the slope formula to prove that there are two pairs of parallel sides. Next, she uses the distance formula to prove that all sides are equal. What additional step must Lydia perform before reaching a conclusion that the quadrilateral is a square?
A) Use the distance formula to prove that the diagonals of the quadrilateral are not equal.
Eliminate
B) Use the slope formula to prove that four right angles exist as a result of perpendicular sides.
C) Use the midpoint formula to prove that the diagonals of the quadrilateral do not bisect each other.
D) Use the Pythagorean Theorem to prove that the diagonals of the quadrilateral are twice the length of each side.