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Overview
Mathematics at Work 12
Geometry
3. Solve problems involving triangles, quadrilaterals, and regular polygons
3.5 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.
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Learning resources
NS Curriculum Aligned