• identify angles as measures of turn and compare angles with right angles in everyday situations.
• We are learning to identify, name, and describe different types of angles (right, acute, and obtuse) and understand their basic properties.

• I can identify and name right angles, acute angles, and obtuse angles.
• I can compare angles and describe them using correct mathematical language.
• I can find examples of different angles in my environment.
• I can use a ruler or other tools to draw different types of angles accurately.

WALT

Success Criteria

An Introduction to Types of Angles

Angles can be seen everywhere!

An angle is the space between two straight lines that start at the same

point. If you stand on one spot and turn to face in another direction, you

have turned through an angle.

Angles measure between 0° and 360°. ° is the symbol we use for degrees.

Right Angles

A right angle is the angle you turn through when you

make a quarter turn.

A right angle is found at the corner of a square or

rectangle. It measures 90°.

We see right angles everywhere - for example on doors,

on books and windows. Look out for right angles around you!

90°

There are 4 right angles or 4 quarter turns in a full turn - that’s 360°.

Right angles are sometimes  marked by a small square tucked

into the right angle.

Right Angles

Which of these are right angles?

a

b

c

f

e

d

√

×

×

√

√

×

Acute Angles

An acute angle is less than 90°. It is smaller than a right angle.

a

b

c

f

e

d

×

√

√

×

√

×

Which of these angles is acute?

Obtuse Angles

An obtuse angle is more than 90° but less than 180°. It is greater

than a right angle.

a

b

c

f

e

d

×

√

√

×

√

×

Which of these angles is obtuse?

Straight Angles and Reflex Angles

A straight angle is when the arms of the angle lie in a straight line.

It measures 180°.

A straight angle is the angle you turn when you make a half turn.

A reflex angle is bigger than a straight angle. It measures more than 180°

but less than 360°.

Complementary Angles

Complementary angles add together to form

a right angle or 90°.

If you know one complementary angle in a right angle you can subtract

it from 90° to find the other.

Find the complementary angles.

30°

?

45°

?

?

25°

65°

45°

60°

20°

70°

Supplementary Angles

Supplementary angles add together to form a straight line or 180°.

If you know one supplementary angle on a straight line you can subtract

it from 180° to find the other.

Find the supplementary angles.

150°

?

85°

?

?

40°

140°

95°

30°

110°

70°

Measuring Angles

We can use a protractor to measure angles.

First, put the centre of the protractor on the vertex of the angle you

are measuring.

Next, line up one side of the angle with the zero line of the protractor

(the line with the number 0).

The other side of the angle will cross the number scale on the protractor

showing the degrees or the measurement of the angle.

Drawing Angles

We can use a protractor to draw angles too.

First, using a ruler, draw a straight line.

Next, place the centre of the protractor at one end of the line. This point

will become the vertex or corner of the angle you are making. Make sure

the line you have drawn lines up with the base line of the protractor

(the line marked 0°).

If you want to draw an angle of 70° look for 70° on the protractor. There

are two number scales on the protractor - on the inside and on the outside.

Make sure you are using the correct scale! Mark a dot or line at 70° at the

edge of the protractor.

It’s important to check your angle once you

have drawn it. Make sure you measure it with

your protractor again.