Explore: Plot the vertices on a coordinate plane.
Plan:
If the diagonals are perpendicular, then ABCD is either a rhombus or a square.
The diagonals of a rectangle are congruent. If the diagonals are congruent and perpendicular, then ABCD is a square.
Solve:
Use the Distance Formula to compare the lengths of the diagonals.
The distance formula is .
(Substitute )
(Simplify)
(Substitute )
(Simplify)
Use slope to determine whether the diagonals are perpendicular.
The slope formula is .
Slope of (Substitute )
Slope of (Substitute )
Since the slope of is the negative reciprocal of the slope of , the diagonals are perpendicular. and have the same measure, so the diagonals are congruent. ABCD is a rhombus, a rectangle, and a square. ABCD is a rhombus, a rectangle, and a square.
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