Skill: Classify triangles by angles

To classify a triangle by its angles, look at the measure of each interior angle.

• Acute triangle: All three angles are less than $90^\circ$.
• Right triangle: One angle is exactly $90^\circ$.
• Obtuse triangle: One angle is greater than $90^\circ$.

The triangle’s position, shape direction, or side lengths do not matter. Focus only on the angle measures.

Example: A triangle has angles measuring $45^\circ$, $90^\circ$, and $45^\circ$.

1. Look at the angle measures: $45^\circ$, $90^\circ$, and $45^\circ$.
2. One angle is exactly $90^\circ$.
3. Therefore, the triangle is a right triangle.

$$\boxed{\text{The triangle is a right triangle.}}$$