Page 56 - Mathematics Coursebook

5.1 Labelling and estimating angles

) Exercise 5.1

1 This diagram shows triangle ABC. A
a Sketch the triangle. b Mark angle CBA.
c Give a three-letter name for each of the other two angles.

2 Say whether each of these angles is acute, right, obtuse or reflex. B C
a b c

d e f

3 Here are the sizes of some angles. Say whether each one is acute, right, obtuse or reflex.

a 120° b 60° c 200° d 300° e 10° f 170°

4 Angle ABC is a right angle. A D
Angles ABD and DBC are equal.

Find the size of:
a angle ABD
b reflex angle ABC

c reflex angle ABD B C

d reflex angle CBD.
5 Every angle in each of the triangles in this diagram is 60°. A B
Find the size of these angles.

a ABC
b AMC
c MDE F M C

d reflex angle BMD

e reflex angle AMF

E D

6 Each of these angles is a multiple of 30°. State the size of each one. Do not measure the angles.

b° c° f °
d°
a°
e°

5 Angles 55