Lines a, b, and c have these features: a || b with transversal c.[br]Congruent Angle Theorems:[br] Vertical Angles, Corresponding Angles, Alternate Interior Angles, Alternate Exterior Angle[br]Supplemental Angle Theorems:[br] Interior Angles on Same Side, Exterior Angles on Same Side[br]Linear Pair Theorems (form straight line):[br] Adjacent Angles at a point[br][br]Move one slider at a time, make observations Congruent Angles should be equal in size. The Supplemental Angles/Linear Pairs should add to be 180°.

Points A, B, C, E, and F can be moved by the user to change the orientation of the parallel lines and the transversal. Points G and H are the intersection points of the transversal and the parallel lines. Points B and D must stay to the right of Points G and H for the demonstration works.