From the Sketch section of the action bar, click Bisecting Line
.
Select two lines.
An infinite bisecting line is created.
Tip:
The bisecting line corresponds to a line symmetrically constrained
to two lines provided that you have previously selected the Geometrical Constraints
in the Sketch section of the action bar.
Note:
If both the selected
lines are parallel to each others, a new line is created
between these lines.