2. Angles formed by transversal lines

If a transversal line meets two lines (parallel or unparalleled lines), eight angles are formed at the points of intersection as shown in the below figure.

 

 

The pairs of angles \(∠1\), \(∠2\); \(∠3\), \(∠4\); \(∠5\), \(∠6\) and \(∠7\), \(∠8\) are linear pairs.

Besides, the pairs \(∠1\), \(∠3\); \(∠2\), \(∠4\); \(∠5\), \(∠7\) and \(∠6\), \(∠8\) are vertically opposite angles.

 

We can further classify the angles into different categories as follows: