Bombay Cambridge GurukulSTD. : VI

Bombay Cambridge Gurukul

MATHEMATICS

Contents

• Angles in daily life

• What is an angle?

• Naming an angle

• Measurement of angle

• Types of angle: Right angle Obtuse angle Acute angleStraight angle

• Test Yourself - 1

• Congruent angles• Pairs of angles: Types

• Test Yourself - 2 • Pairs of angles

formed by a transversal

• Test Yourself - 3

If we look around us, we will see angles everywhere.

Angles In Daily Life

Common endpoint

B C

B

A

Ray BC

Ray BA

Ray BA and BC are two non-collinear rays

When two non-collinear rays join with a common endpoint (origin) an angle is formed.

What Is An Angle ?

Common endpoint is called the vertex of the angle. B is the vertex of ÐABC.

Ray BA and ray BC are called the arms of ÐABC.

Fact: We can also think of an angle formed by rotating one ray away from its initial position.

To name an angle, we name any point on one ray, then the vertex, and then any point on the other ray.

For example: ÐABC or ÐCBA

We may also name this angle only by the single letter of the vertex, for example ÐB.

A

BC

Naming An Angle

Angles are accurately measured in degrees.

Protractor is used to measure and draw angles.

Measurement Of An Angle

There are four main types of angles.

Straight angle

Right angle Acute angle Obtuse angle

A

B C

A

B C

A

B C

BA C

Types Of Angles

Right angle: An angle whose measure is 90 degrees.

Right Angle Acute AngleStraight Angle Obtuse Angle

Examples Of Right Angle

Obtuse angle: An angle whose measure is greater than 90 degrees.

Right Angle Acute AngleStraight Angle Obtuse Angle

Examples Of Obtuse Angle

Acute angle: An angle whose measure is less than 90 degrees.

Right Angle Acute AngleStraight Angle Obtuse Angle

Examples Of Acute Angle

Straight angle: An angle whose measure is 180 degrees.

Right Angle Acute AngleStraight Angle Obtuse Angle

Examples Of Straight Angle