How_To_Be_Good_At_Math

GEOMETRY • TYPES OF ANGLE 233

Types of angle

As well as the right angle, there are other important kinds

of angle that we name according to their size.

Acute angle

When an angle is less

than 90°, we call it an

acute angle.

Right angle

A quarter turn is

exactly 90°. We call it

a right angle.

Obtuse angle

An angle that's more

than 90° but less than 180°

is an obtuse angle.

Reflex angle

An angle that's

between 180° and 360°

is called a reflex angle.

Straight angle

An angle of

exactly 180° is called

a straight angle.

0°

90°

180°

240°

90°

0°

The arm turns

anticlockwise to

make a 45° angle

90°

180° 0°

Right angle (90°)

90°

0°

135°

90°

180° 0°

180°

180°

232_233_right_angles_angle_sizes.indd 233 29/02/2016 18:05