 Manipulative 1: Parallel lines. Created with GeoGebra. 

In Euclidean geometry, two
coplanar
lines are parallel if they do not
intersect.^{[1]}
In metric geometries, parallel lines have the same slope. Since two lines
with the same
slope
have the same rate of change, for any change in x
corresponds to an identical change in y. This means that the lines will always be the same
distance apart and will never intersect. Click on the blue points in manipulative 1
and drag them to change the figure.
