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Included Angle
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
An included angle is the angle formed between two given sides of a triangle (or polygon).
Key points:
It is the angle directly between two sides.
For example, in triangle ABC, if the given sides are AB and AC, then ∠A is the included angle.
The concept of included angle is important in congruence theorems like SAS (Side-Angle-Side) and ASA (Angle-Side-Angle).
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