Exercise 6 Page 427

Let's consider the possible linear pairs and vertical angles one at a time.

Linear Pair

Two angles form a linear pair when they are both adjacent and supplementary. If a straight angle is divided into two angles, those angles form a linear pair. Let's look at an example.

In the above diagram, ∠ 1 and ∠2 form a linear pair. Since all the straight angles in the given figure are divided into three angles there is no linear pair.

Vertical Angles

Two angles are said to be vertical if their sides form two pairs of opposite rays.

We have three such pairs in the given figure. ∠ 1 and ∠ 4 ∠ 2 and ∠ 5 ∠ 3 and ∠ 6