Triangle Classification by Angles

About This Diagram

This diagram shows the three classifications of triangles based on their angle measures.

Triangle Types by Angles

Type	Definition	Properties
Acute	All three angles less than 90°	"Pointed" appearance
Right	Exactly one 90° angle	Right angle marked with square; hypotenuse is longest side
Obtuse	Exactly one angle greater than 90°	"Wide" appearance; other two angles must be acute

Visual Markers

Arc marks at angles show the angle measurements
Right angle square (small square symbol) indicates a 90° angle
Larger arcs indicate obtuse angles (>90°)

Key Facts

Every triangle falls into exactly ONE of these classifications by angle
A right triangle always has exactly one 90° angle
An obtuse triangle can only have one obtuse angle (the other two must be acute)

Interaction

Click on any triangle panel to highlight that type and dim the others.

Learning Objectives

Remember the three angle-based classifications
Understand how angle measures determine triangle type

Bloom's Taxonomy Level

Remembering and Understanding - Terminology introduction.

Iframe Embed Code

<iframe src="https://dmccreary.github.io/geometry-course/sims/triangle-classification-angles/main.html"
        height="452px"
        width="100%"
        scrolling="no"></iframe>