Parallel Lines and Ratio Proof

Parallel lines have many important properties that you have to memorize in order to be successful in proving problems. In this post, we will discuss the properties of parallel lines intersecting two other lines. We are going to show the relationship among three parallel lines intersecting two lines. In the figure below, parallel lines l, m, […]
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Quadrilateral with Congruent Opposite Sides are Parallelogram

This is the first of a series of post about the conditions of a quadrilateral to be a parallelogram.  In this post, I will be discussing the proof that if the opposite sides of a quadrilateral are congruent, then it is a parallelogram. Given Quadrilateral  
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Proof That The Opposite Sides of a Parallelogram Are Congruent

A parallelogram is a quadrilateral whose opposite sides are parallel. In the figure below, is a parallelogram. is parallel to and is parallel to .   In this post, aside from being parallel, we will also prove that the opposite sides of a parallelogram are congruent.
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