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Angle-Side-Angle (ASA) Congruence Theorem
See It in Action
Two examples of the idea done right—and one common look-alike that is not right.
EXAMPLE
EXAMPLE
NON-EXAMPLE
Definition
The Angle-Side-Angle (ASA) Congruence Theorem states:
If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the two triangles are congruent.

Key points:
The side must be between the two angles.
This guarantees that the shape of the triangle is fixed, so the triangles must be congruent.
Video
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