Proving a Quadrilateral a Parallelogram | Geometry Proof
This video geometry lesson proves two parallelogram theorems.
If the diagonals of a quadrilateral bisect each other, then the quadrilateral is a parallelogram.
Proof 1: If both pairs of opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram.
Theorems Used: If both pairs of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram and If one pair of opposite sides of a quadrilateral is both congruent and parallel, then the quadrilateral is a parallelogram to solve problems.
Special Parallelograms Part 2 Rhombus and Rectangle Proofs
This video uses the two column method to prove two theorems.
Proof 1: The diagonals of a rectangle are congruent. This amounts to be a triangle proof to use CPCTC.
Proof 2: The diagonals of a rhombus are perpendicular.
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