How to mark parallel lines, how to show lines are parallel, and how to compare skew and parallel lines.
How to determine whether two lines in space are parallel or perpendicular.
How to identify parallel lines, a line parallel to a plane, and two parallel planes.
How to define and label a line segment.
How to construct a perpendicular line at a point on a line.
How to use standard form of a line.
How to take the converse of the parallel lines theorem.
How to find the vector and parametric equations of a line when given two points on the line.
How to find the angle of inclination of a line.
How to use point-slope form of a line.
How to find the shortest distance between a point and a line.
How to graph a line in slope-intercept form.
How to write the vector equation of a line.
How to find the polar equation of a line through the origin (or pole).
How to write the parametric equations of a line segment that goes from point A to point B.
How to prove two triangles are similar using a line parallel to a base.