Proving Parallelograms With Two Column Proofs – Geometry

This geometry video tutorial provides a basic introduction into two column proofs with parallelograms. It explains the different ways of proving parallelograms. Here are five ways: 1. opposite sides must be parallel. 2. Opposite sides must be congruent. 3. opposite angles must be congruent. 4. 1 opposite side may be both parallel and congruent. 5. Diagonals must be perpendicular bisectors of each other. This video contains plenty of examples and practice problems. Here is a list of theorems used in these two column proofs: reflexive property, vertical angle theorem, definition of a parallelogram, definition of a midpoint, definition of a segment bisector, addition property of equality, substitution property of equality, definition of congruent segments, segment addition, SAS postulate, ASA postulate, and CPCTC.

Polygons: https://www.youtube.com/watch?v=E_-3ulbtcLk

Angles of Regular Polygons:

Quadrilaterals:

Parallelograms:

Rectangles – Special Quadrilaterals:

Isosceles Trapezoids:

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The Rhombus:

Kites:

Proving a Quadrilateral Is a Kite:

Proving a Quadrilateral Is a Rhombus:

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Proving Isosceles Trapezoids:

2 Column Proofs – Quadrilateral:

Skew Lines:

Points, Lines, Planes, & Segments:

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