Shape and Space

DEGREE

DEGREE

We use degrees (e.g. 90°) to measure angles

Right Angle(90°)

Straight Line(180°)

Full Turn(360 °)

Acute Angle(less than 90°)

Obtuse Angle(less than 180°, more than 90°)

Reflex Angle(less than 360°, more than 180°)

EXERCISES

Describe the following as:

a) Right Angle b) Straight Line c) Acute Angle d) Obtuse Angle e) Reflex Angle

3) 4)

5)6)

7) 8)

9)

10)11)

1) 2)

MEASURING ANGLES

We use a PROTRACTOR to measure angles.

A protractor has a clockwise and anticlockwise scale

If an angle turns (opens) clockwise

you must use the external scale

If an angle turns (opens) anticlockwise

you must use the internal scale

MEASURING ANGLES

Step 1: Put the centre of the

protractor on the corner of the angle

Step 2: Turn the protractor so that

0° is on one of the lines

Step 3: Start to count in the direction

of the angle 10°, 20°, 30° etc 10°

20°

30°

50°

40°

70°60°

0°

Cwblhewch y taflenni gwaithComplete the worksheets

CREATING A 70° ANGLE

Step 1: Put the centre of the

protractor on the end of a straight line

Step 2: Turn the protractor so that

0° is on the line

Step 3: Start to count in the direction

of the angle 10°, 20°, 30° etc

Step 4: Put a dot on 70°

Step 5: Connect the dot with the end

of the straight line

10°

20°

30°

50°

40°

70°60°

0°

70°70°

EXERCISES

Using a Protractor and Ruler,

create these angles in your books.

Label each angle like this :-

a) 60°b) 45°c) 130°d) 145°e) 75°

f) 105°g) 57°h) 168°i) 23°

35°

STRAIGHT LINE (180°)

We don’t always find angles by measuring. We can calculate angles.

Angles on a straight line add to 180°

80°a

a = 180° – 80°a = 100°

162°b

b = 180° – 162°b = 18°

EXERCISES

Calculate the angles labelled with letters

50°a

138°

cb65°

d

117°

72°e

103°f

30°g

20°

50°

h100°

i

64°

FULL TURN (360°)

We don’t always find angles by measuring. We can calculate angles.

Angles around a point make a full turn.

They add to make a total of 360°

290°

a

235°b

a = 360° – 290°a = 70°

b = 360° – 235°b = 125°

EXERCISES

Calculate the angles labelled with letters

285°

a82°

b

c

32°

d24°

130°

e

170°

147°

f

g

156°44°

h

88°134°

OPPOSITE

We don’t always find angles by measuring. We can calculate angles

The OPPOSITE angles are equal. This happens when two lines cross each other.One RED ANGLE and one BLUE ANGLE add to 180°

120°

60° q

p

150°x

zy

q = 60°p = 120°

y = 150°x = 30°z = 30°

EXERCISES

Calculate the angles labelled with letters

a 40°135°

b

cd

145°35°

29°151°

fe40°

i

g

h

150°

kL j

35°

m

n o 77°pq

r

tu

s