Identify acute, right, obtuse, and straight angles

An angle is classified by the size of its opening, measured in degrees: acute angles are less than 90°, right angles equal 90°, obtuse angles are greater than 90° but less than 180°, and straight angles equal 180°. The classification depends on the rays’ relationship rather than their orientation or length, supporting analysis of polygons and angle relationships.

Detailed Explanation: Identify acute, right, obtuse, and straight angles

To classify an angle, look at its measure in degrees. Compare it with $90^\circ$ and $180^\circ$ :

Acute: less than $90^\circ$
Right: exactly $90^\circ$
Obtuse: greater than $90^\circ$ but less than $180^\circ$
Straight: exactly $180^\circ$

Example

Classify an angle that measures $125^\circ$ .

Compare $125^\circ$ with $90^\circ$ :

125^\circ > 90^\circ

Compare $125^\circ$ with $180^\circ$ :

125^\circ < 180^\circ

Therefore, $125^\circ$ is greater than $90^\circ$ but less than $180^\circ$ .

Answer: The angle is obtuse.

The direction the angle points and the lengths of its rays do not change its classification. Only the size of its opening matters.

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Angles - Acute, Obtuse, Right or Straight

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