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# Side Angle Side Theorem

## Side Angle Side Theorem Lesson

### The Theorem for Congruence — SAS

Abbreviated as SAS, the side angle side theorem tells us:
If two triangles have two congruent sides and a congruent angle, then the triangles are congruent.

Let's look at theoretical triangles T1 and T2. T1 has two sides measured to be 3 and 5 long and an angle measured to be 90°. T2 also has two sides measured to be 3 and 5 long and an angle measured to be 90°. The SAS Theorem tells us that T1 and T2 must be congruent because they have two side lengths in common and an angle measurement in common.

INTRODUCING

### When do we use the Side Angle Side Theorem?

The SAS Theorem is especially useful for saving time when finding the third side and other two angles of a triangle if there is a congruent triangle where those values are already known.

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