Texas Instruments
Texas Instruments: Finding the Shortest Path
Students discover the shortest distance light travels from an object to the human eye, as the light from the object reflects off a single mirror. In the process they learn about reflection in a line, congruent angles, angle bisectors,...
Math Open Reference
Math Open Reference: Congruence
A complete reference guide to congruence including congruent triangles and polygons. It provides definitions, animation, and interactive activities that enhance further explanation.