Learn Math [Form 3]

Chapter 1 - Lesson 1

CHAPTER 1: LINES AND ANGLES (II)

1.1 Properties of Angles Associated with Transversals and Parallel Lines

Identifying transversals, corresponding angles, alternative angles and interior angles

A transversal is a straight line that intersects two or more straight lines.
Example

In the figure, PQ is a transversal. When it intersects two parallel lines RS and TU, three types of angles are formed.
(a) Corresponding angles:
      a and b, e and f
      c and d, g and h
(b) Alternate angles:
      b and g, e and d
(c) Interior angles (or allied angles):
      b and e, d and g

MATHS ALERT!

Identifying the properties of angles associated with parallel lines

By using a protractor or acetate overlays (tracing paper), we can show that the following are true.

When a transversal intersects two parallel lines,
(a) the corresponding angles are equal,
(b) the alternate angles are equal, and
(c) the interior angles are supplementary; the sum of the interior angles is 180°.