## 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 T_{1} and T_{2}. T_{1} has two sides measured to be 3 and 5 long and an angle measured to be 90°. T_{2} also has two sides measured to be 3 and 5 long and an angle measured to be 90°. The SAS Theorem tells us that T_{1} and T_{2} 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.