Classify triangles by sides and angles
Triangles are the simplest polygons - shapes with 3 sides and 3 angles.
| Type | Description | Example |
|---|---|---|
| Equilateral | All 3 sides equal | △ with sides 5, 5, 5 |
| Isosceles | 2 sides equal | △ with sides 5, 5, 3 |
| Scalene | No sides equal | △ with sides 3, 4, 5 |
| Type | Description |
|---|---|
| Acute | All angles less than 90° |
| Right | One angle exactly 90° |
| Obtuse | One angle greater than 90° |
The sum of interior angles in ANY triangle is 180°.
An exterior angle equals the sum of the two non-adjacent interior angles.