# Congruent Figures: Dynamic Illustration

Recall a RIGID MOTION is a transformation that preserves distance. So far, we have already explored the following rigid motions:
Translation by Vector
Rotation about a Point
Reflection about a Line
For a quick refresher about rigid motions, see this Messing with Mona applet.

## CONGRUENT FIGURES

**Definition: Two plane figures are CONGRUENT if and only if one can be mapped perfectly onto the other using any 1 or sequence of 2 (or more) RIGID MOTIONS (translations, reflections, and/or rotations).**The applet below dynamically illustrates,

**by DEFINITION**, what it means for any 2 figures (in this case, triangles) to be

**CONGRUENT.**Feel free to move the BIG WHITE VERTICES of either triangle anywhere you'd like at any time.

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