Two triangles are congruent when they have the same shape and size. That means their corresponding sides are of equal length and their corresponding angles are of equal measure.

Two triangles are similar when they have the same shape. That means their corresponding angles are equal and that the length of corresponding sides are scaled by a common scale factor.

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Definition

SSS Congruence Rule

AAS Congruence Rule

ASA Congruence Rule

SAS Congruence Rule

HL Congruence Rule

Congruent Triangles

Two triangles are congruent if they have the same shape and size. Their corresponding sides and angles are of equal length and measure. This video lays out why. 

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What Are Congruent Triangles?

The SSS or Side-Side-Side congruence rule states that if two triangles have sides all of equal lengths, they must be congruent. This video's examples explain.

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What Is the SSS Congruence Rule?

The Angle-Angle-Side congruence rule allows a determination of congruence if you have two corresponding angles and a non-included side. This video explains. 

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What Is the AAS Congruence Rule?

The ASA congruency rule can determine if two triangles are congruent if you have information about two angles and their included side. This video explains. 

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What Is the ASA Congruence Rule?

The SAS congruency rule states that two triangles are congruent if two of their corresponding sides and their included angle are congruent. This video explains. 

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What Is the SAS Congruence Rule?

This video on the Hypotenuse-Leg congruence rule shows that two triangles are congruent if you know the lengths of the hypotenuses and two corresponding legs. 

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