Triangles
Overview
Expect to see questions that test your understanding of triangles and their properties. In this section we’ll cover the following:
 Triangle Basics
 Classifying Triangles by Angle
 Classifying Triangles by Side
 Triangle Theorems
Let’s look at each of these in more detail:
Triangle Basics
What is a triangle? Look at these definitions.
Despite their common properties, triangles come in different sizes and angle measures. and they can be categorized by side lengths and angle measures. To review triangle basics, click on this link. It is a presentation that goes over this topic.
Classifying Triangles by Angles
Depending on the angle measures that make up a triangle, the result is a specific type of triangle. Here are the different classifications of triangles by angle:
 A triangle with three acute angles is called an acute triangle.
 A triangle with one acute angle is called an obtuse triangle. A triangle can only have one obtuse angle.
 A triangle with a right angle is called a right triangle. A triangle can only have one right angle.
 A triangle two congruent angles is an isosceles triangle.
 A triangle three congruent angles is an equilateral triangle.
To learn more about classifying triangles by angle measures, click on this link. It is a presentation that goes over this topic.

Classifying Triangles by Side Length
In addition to classifying triangles by the type of angles that make it up, it’s also possible to classify triangles by their side lengths.
 A triangle with three sides that are of different lengths is called a scalene triangle.
 A triangle with two sides that are the same length is called an isosceles triangle.
 A triangle with three sides that are the same length is called an equilateral triangle.
 A triangle whose sides align with the Pythagorean Theorem is a right triangle.
To learn more about classifying triangles by side lengths, click on this link. It is a presentation that goes over this topic.

Triangle Theorems
Make sure you are familiar with these key triangle theorems. They will often be part of solving a particular SAT problem involving triangles.
Click on this link to see a slide show of these theorems.

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