### Theory:

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:
1. The corresponding angles

2. The alternate Interior angles

3. The alternate Exterior angles