2 lines that are intersected by a third line known as a transversal.

Illustration used to prove the theorem "If three or more parallel lines intercept equal segments on…

The cross-ratio of four points in a line is equal to the cross-ratio of their projections on any other…

Illustration that shows if two parallel lines are cut by three or more transversals that pass through…

Illustration that shows if two parallel lines are cut by three or more transversals that pass through…

Illustration showing that a transversal is a straight line that cuts two or more straight lines.

Illustration showing that when three or more parallel lines intercept equal parts on one transversal,…

Illustration showing that if two parallel lines are cut by a transversal, then the alternate interior…

Illustration showing that when two straight lines in the same plane are cut by a transversal, if the…

Illustration showing that when two parallel lines are cut by a transversal, the exterior-interior angles…

Illustration showing that when two parallel lines are cut by a transversal, the two interior angles…

Illustration showing two parallel vertical lines cut by a perpendicular line and a transversal. Congruent…

Illustration used to prove the theorem, "If two straight lines are cut by a transversal making a pair…

Illustration used to prove the theorem, "If two parallel lines are cut by a transversal, the alternate…

Illustration of two straight lines cut by a transversal. The 8 angles formed are labeled.

Illustration of two straight lines, AB and CD, cut by a transversal EF.