Definitions of quadrilateral and parallelograms

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DEFINITIONS Quadrilaterals et al

Abstract This is a short booklet that looks at the definition of a quadrilateral, parallelogram, angles, and right angles.

Genny Phillips

Image from thecollaboratory.wikidot.com and licensed under CC0 Public Domain

What is a quadrilateral?

That’s easy!

A quadrilateral is a shape that has 4 sides.

This is a quadrilateral: Quad means 4 and lateral means side.

The sides of a quadrilateral are line segments.

What is a line segment?

This is a line segment!

A line segment is just a part of a line.

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What is a parallelogram?

A parallelogram is a special type of quadrilateral.

It has 4 sides, and the opposite sides are parallel.

The figure on the left is a parallelogram.

The sides opposite each other are parallel. *Remember parallel means that lines or segments never cross.

The opposite sides of a parallelogram are also congruent.

Congruent means they have the same length or equal measure.

So, in the figure on the left, the red sides are parallel and have the same length. The green sides are also parallel and they have the same length.

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So, what’s this about interior and exterior?

Exterior

Exterior

Interior

Exterior

Exterior

Interior means inside. So, the blue pattern region is the interior of the parallelogram.

Anything not in the interior is in the exterior or outside.

So, what’s your angle?

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Well, it’s not just my angle, it could belong to anybody!

An angle is created by 2 segments that intersect.

For example, in a quadrilateral, the corners are angles.

This is an angle.

A quadrilateral has 4 angles because it has 4 sides!

Okay, an angle is at a corner of the quadrilateral.

When is an angle a right angle?

Okay, I could say it is right because it’s never wrong.

Seriously though, a right angle is formed when the sides or segments that meet at the corners are perpendicular.

PERPENDICULAR???

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It’s all good!

Perpendicular just means that the sides of the quadrilateral meet to form an angle that has a measure of 90°.

Like this:

The red boxes mean the sides are perpendicular and the angles at the corners are right angles.

Right angles measure 90°.

Written by Genny Phillips using Microsoft Word.

3/29/17