Step 1: Recall what is exterior angle

NOTE: An exterior angle of a polygon is an angle outside the polygon

formed by one of its sides and the extension of an adjacent side.

Step 2: Calculate the exterior angles of the triangle at each vertex.

NOTE: The **exterior angle theorem** states that the exterior angle formed

when you extend the side of a triangle is equal to the sum of its

non-adjacent angles. Remember, our non-adjacent angles are

those that don't touch the angle we are working with.

Step 3: Add all the exterior angles of the triangle.

NOTE: If you count one exterior angle at each vertex, the *sum* of the

measures of the *exterior angles* of a polygon is always 360°.