Page 1 - Acute, right and obtuse angles

SAI International School

Class – III

LN – Acute, right and obtuse angles

Lesson Objectives:

By the end of the lesson, students should be able to:

1. Define acute, right, and obtuse angles.

2. Identify and classify these angles by their measurements.

3. Draw examples of each type of angle using a ruler and protractor.

4. Recognize these angles in real-life situations.

What is an Angle?

An angle is formed when two lines (or rays) meet at a common point called the

vertex.

Types of Angles

Type of Measurement
Description Example
Angle Range

Acute Angle less than a right angle Less than 90° 30°, 45°

Angle that forms a perfect square
Right Exactly 90° 90°
corner

Angle more open than a right Between 90° and 120°,
Obtuse
angle 180° 135°

How to Measure Angles

• Use a protractor to measure an angle in degrees (°).

• Place the centre of the protractor on the vertex.

• Align one side of the angle with the baseline.

• Read the measurement where the second side crosses the scale.