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Mathematics Class 5 - Angles Notes

Comprehensive study notes for Class 5 - Angles olympiad preparation

Angles

Welcome to the chapter on Angles for Class 5. In this chapter, you will learn what angles are, how to name and measure them, and how to identify different types of angles. By the end of this chapter, you will be able to recognize, draw, and measure angles confidently!

Introduction

Angles are formed when two lines meet at a point. The point where they meet is called the vertex. Angles are measured in degrees (°).

Parts of an Angle

  • Arms: The two lines that form the angle.
  • Vertex: The point where the arms meet.

Types of Angles

  • Acute Angle: Less than 90°
  • Right Angle: Exactly 90°
  • Obtuse Angle: More than 90° but less than 180°
  • Straight Angle: Exactly 180°
  • Reflex Angle: More than 180° but less than 360°
  • Complete Angle: Exactly 360°

Measuring Angles

Angles are measured using a protractor. Place the center of the protractor at the vertex and read the number where the other arm points.

  • Example: If the arm points to 60°, it is a 60° angle.

Naming Angles

Angles are named using three letters. The middle letter is always the vertex.

  • Example: ∠ABC, where B is the vertex.

Angles in Real Life

  • Corners of a book (right angle)
  • Hands of a clock (different angles)
  • Open doors (acute, right, or obtuse angles)

Fun Activity: Angle Hunt!

Look around your home or classroom. Find and draw objects that show different types of angles!

Summary

  • Angles are formed when two lines meet at a point.
  • There are different types of angles: acute, right, obtuse, straight, reflex, and complete.
  • Angles are measured in degrees using a protractor.

Practice Questions

  1. What is the vertex of an angle?
  2. Name an angle that is less than 90°.
  3. How many degrees are in a right angle?
  4. What tool is used to measure angles?
  5. Draw and name three types of angles.

Challenge Yourself

  • Find and measure three angles in your classroom using a protractor.
  • Draw a clock showing 3 o’clock and measure the angle between the hands.

Did You Know?

  • A triangle has three angles!
  • Angles are used in art, sports, and building things.

Glossary

  • Angle: The space between two lines that meet at a point.
  • Vertex: The point where two lines meet.
  • Protractor: A tool used to measure angles.
  • Degree (°): The unit for measuring angles.

Answers to Practice Questions

  1. The point where two lines meet.
  2. Acute angle.
  3. 90°.
  4. Protractor.
  5. (Drawings will vary: acute, right, obtuse, etc.)

Practice drawing and measuring angles to become an angle expert!

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