Properties

In this section, we will discuss only important properties as most of the basic properties are very easy and there is no need to waste time on them. Starting with Intersecting lines, in the figure below, Lines AB and CD intersect at a point forming four angles  ∠1, ∠2, ∠3 & ∠4.

a) Sum of the linear pairs is 180° like in figure ∠1 + ∠2 = 180°.

b) Vertically opposite angles are equal like in figure ∠1 = ∠3.

Parallel Lines

If two parallel lines AB and CD are intersected by a transversal t, then each pair of corresponding angles, each pair of alternate interior angles, alternate exterior angles are equal. And the sum of any two unequal angles is 180°.