How to define and label a line segment.
How to construct a perpendicular line at a point on a line.
How to mark parallel lines, how to show lines are parallel, and how to compare skew and parallel lines.
How to identify parallel lines, a line parallel to a plane, and two parallel planes.
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 graph a line in slope-intercept form.
How to find the shortest distance between a point and a line.
How to determine whether two lines in space are parallel or perpendicular.
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.