Page 62 - Mathematics Coursebook

5.4 Solving angle problems

3 Lines WX and YZ are parallel.
W Y

77°

c° a°
b°

X Z

One angle of 77° is marked. Find the values of a, b and c.
4 This diagram shows four identical triangles.

A

Look at the angles at point A.
Explain why this shows that the angles of a triangle add up to 180°.
5 ABC is an isosceles triangle. AB = BC and angle BAC = 40°.
B An isosceles triangle
has two equal sides and
two equal angles.
A

C
Calculate the other two angles of the triangle.
6 Calculate the value of a.

45°
a°

60°

7 Explain why AB and AC are equal in length.

C
72°
A 36°

B

5 Angles 61