Rigid motions are at the foundation of the definition of congruence. Students reason from the basic properties of rigid motions (that they preserve distance and angle), which are assumed without proof. Rigid motions and their assumed properties can be used to establish the usual triangle congruence criteria, which can then be used to prove other theorems.

## Collection Contents

### Quiz - Congruence, Proof, and Constructions Cluster: Understand congruence in terms of rigid motions: Standards: G.CO.6, G.CO.7, G.CO.8

by Allen Wolmer

Standards: G.CO.6, G.CO.7, G.CO.8
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### G.CO.6 Use geometric descriptions of rigid motions to transform figures

by Allen Wolmer

Use geometric descriptions of rigid motions to transform figures and to predict the effect of a given rigid motion on a given figure; given two figures, use the definition of congruence in terms of rigid motions to decide if they are congruent.
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### G.CO.7 Use the definition of congruence in terms of rigid motions to show that two triangles are congruent

by Allen Wolmer

Use the definition of congruence in terms of rigid motions to show that two triangles are congruent if and only if corresponding pairs of sides and corresponding pairs of angles are congruent.
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### G.CO.8 Explain how the criteria for triangle congruence (ASA, SAS, and SSS) follow from the definition of congruence in terms of rigid motions.

by Allen Wolmer

G.CO.8 Explain how the criteria for triangle congruence (ASA, SAS, and SSS) follow from the definition of congruence in terms of rigid motions.
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