Parallel lines are lines that do not intersect.
The complete proof and reason is:
- [tex]\mathbf{ \angle\ 1\ \cong\ \angle\ 2}[/tex] ----- Given
-
[tex]\mathbf{ \angle\ 1\ and \ \angle\ 3\ are\ vertical}[/tex] ------ Definition. of vertical angles
- [tex]\mathbf{ \angle\ 1\ \cong\ \angle\ 3}[/tex] ------ vertical angle theorem
- [tex]\mathbf{ \angle\ 2\ \cong\ \angle\ 3}[/tex] ---- transitive property
-
[tex]\mathbf{a\ ||\ b}[/tex] ------ converse of corresponding angles theorem
From the question, we are given that:
[tex]\mathbf{ \angle\ 1\ \cong\ \angle\ 2}[/tex] ----- this represents the first statement
So, the second statement is:
[tex]\mathbf{ \angle\ 1\ and \ \angle\ 3\ are\ vertical}[/tex]
Because they are vertical angles, then they are congruent.
So, we have:
[tex]\mathbf{ \angle\ 1\ \cong\ \angle\ 3}[/tex]
Transitive property states that:
[tex]\mathbf{ if \ a = b\ and\ b = c, \ then\ a = c}[/tex]
In (1), and (2), we have:
[tex]\mathbf{ \angle\ 1\ \cong\ \angle\ 2}[/tex] and [tex]\mathbf{ \angle\ 1\ \cong\ \angle\ 3}[/tex]
This means that:
[tex]\mathbf{ \angle\ 2\ \cong\ \angle\ 3}[/tex]
At this point, we have proved that both lines are parallel.
i.e.
[tex]\mathbf{a\ ||\ b}[/tex]
Read more about parallel lines at:
https://brainly.com/question/16701300