# Classification of Angles – Acute, Obtuse, Right, Straight, Reflex, and Complete Angles

An Angle is the basic concept of Geometry and it is hard to understand geometry without a grip on Angles. Based on the measurement of an angle, the angles are classified into different types. Find detailed notes on the concept of the angle for free on our page. We have given clear details of the Classification of Angles along with solved examples. Get all Lines and Angles Problems for free of cost and improve your preparation level.

## Types of Angles

There are six different types of angles explained below.

1. Acute Angle
2. Right Angle
3. Obtuse Angle
4. Straight Angle
5. Reflex Angle
6. Complete Angle

### 1. Acute Angle

An acute angle is measured when the angle is between 0º but less than 90º. For example, 30º, 60º, 40º are called Acute Angles. From the above figure, ∠ABC represents an acute angle as it consists of less than 90º.
∠ABC < 90º

#### 2. Right Angle

When the angle is equal to 90°, then it is called a right angle. From the above figure, ∠XYZ represents the right angle as it consists of 90º.
∠XYZ = 90º

#### 3. Obtuse Angle

An Obtuse Angle is an angle when the angle is between more than 90° but less than 180°. From the above figure, ∠ABC represents the Obtuse angle as it consists of more than 90º.
∠ABC > 90°
∠ABC < 180°

#### 4. Straight Angle

An angle which is equal to 180° is called a straight angle. From the above figure, ∠AOB represents the Straight angle as it consists of 180º.
∠AOB = 180º

#### 5. Reflex Angle

An angle that consists of more than 180° but less than 360° is called a reflex angle. From the above figure, ∠ABC represents the Reflex angle.
∠ABC > 180°
∠ABC < 360°

#### 6. Complete Angle

An angle that is equal to 360° is called a complete angle.
60 minutes = 1 revolution = 1 complete angle. From the above figure, ∠BAC represents the Complete angle.

### Frequently Asked Questions on Types of Angles

1. The figure shown below is of a straight angle, ∠XOY. Find the missing angle in the given figure? Solution:

∠XOY is a straight angle, that is ∠XOY = 180°
∠XOY = ∠XOZ +∠YOZ
180 = ?+55
? = 180-55
? = 125 °
The missing angle in the above figure: 125°

2. Mention the types of triangles with respect to the angles?

Based on the different angles, the triangles are classified into 5 types. They are the Obtuse Triangle, Right Triangle, Acute Triangle, and Equiangular Triangle.

3. What is an Equilateral Triangle?

An equilateral triangle consists of the same length of sides and has the same measure angles of 60°.

4. What is a triangle?

A triangle is a closed figure that has 3 lines with endpoints. The sum of the interior angle of the triangle is going to be 180°. Also, the sum of the exterior angles is always going to be 360°.

5. Define an obtuse triangle.

An obtuse triangle consists of two acute angles and one obtuse angle. The acute angle is less than 90° and where the obtuse angle is more than 90°.