Obtuse angle

Definition: An angle whose measure is greater than 90° and less than 180°
Try this Adjust the angle below by dragging the orange dot at A and see how the angle ∠ABC behaves. Note that it is obtuse for all angles greater than 90° and less than 180°
Not to be confused with an obtuse triangle which has one obtuse interior angle.

Types of angle

Altogether, there are six types of angle as listed below. Click on an image for a full description of that type and a corresponding interactive applet.

Acute angle Right Angle Obtuse Angle
Acute angle
Less than 90°		 Right angle
Exactly 90°		 Obtuse angle
Between 90° and 180°
Straight Angle Reflex Angle Full Angle
Straight angle
Exactly 180°		 Reflex angle
Between 180° and 360°		 Full angle
Exactly 360°


Other angle topics

General

Angle Types

Angle relationships

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