Overview

Pre-Calculus Elective 11 (MAT521E)

Geometry

1. Demonstrate understanding of basic geometric concepts

1.9 Triangles

Triangles: Definitions, Angle Sum, and Classification

Understand the basic parts of a triangle, how its angles always add up to 180 degrees, and the rule that decides whether three sides can form a triangle at all.

What You'll Learn

Identify the vertices, sides, and interior angles of any triangle using standard labeling conventions.

Apply the triangle angle sum theorem to find a missing angle when two angles are known.

Recognize a median of a triangle and distinguish it from an altitude or a perpendicular bisector.

Test three given side lengths against the triangle inequality theorem to see if they can form a triangle.

Compare triangle classifications by side length and by angle measure as a foundation for congruence and similarity.

This Unit Includes

Learning resources

PEI Curriculum Aligned