Properties of Quadrilaterals

Lesson's Glossary
Lesson's Content
Interactive 1
Interactive 2
Vocabulary Puzzle Interactive

Angle
Geometric shape formed by two rays (initial and ending sides of the angle) that share a common endpoint called the vertex. You may name an angle using the vertex, or a point in each ray and the vertex label in the center.

Parallelogram
Any quadrilateral with two pairs of opposite sides parallel.

Polygon
It is a closed plane figure with a least three straight segments as sides.

Quadrilateral
A four-sided polygon.

Rectangle
A quadrilateral whose angles are all right angles.

Segment
Line segment; A section of a line, defined by two end points and all the points between them.

In a parallelogram, consecutive angles are supplementary. Review this concept here.

Drag point "C" within the shaded area to verify that you have

supplementary angles. Check the sum below the figure.

When working with parallelograms, many times you have to understand

that alternate interior angles are congruent, and that consecutive interior angles

are supplementary.

You may drag point "B" in the below applet to verify these angle relationships.

Parallelograms, and Rectangles: Finding Segments, and Angles.

How often when solving a problem that involves the properties of a parallelogram, have you felt lost?...How is this? Should I state that the angles are congruent, or that they are supplementary? Are the diagonals bisecting each other? How are the two consecutive angles?