Find the value of and the measure of each angle. F 86 ° 8) Q P G 35 ° 95 °? Then either ∠1 is an exterior angle of 4ABRand ∠2 is an interior angle opposite to it, or vise versa. Because an exterior angle is equal to the sum of the opposite interior angles, it follows that it must be larger than either one of them. Remember that every interior angle forms a linear pair (adds up to ) with an exterior angle.) The following diagram shows the exterior angle theorem. The exterior angle dis greater than angle a, or angle b. You can use the Corresponding Angles Theorem even without a drawing. To know more about proof, please visit the page "Angle bisector theorem proof". Set up an equation using the Exterior Angle Theorem. Example 2. Find the values of x and y in the following triangle. I could go like that, that exterior angle is 90. All exterior angles of a triangle add up to 360°. U V 65 ° 3) U Y 50 ° 70 ° ? An exterior angle is the angle made between the outside of one side of a shape and a line that extends from the next side of the shape. Exterior Angle Theorem. They are found on the outer side of two parallel lines but on opposite side of the transversal. Applying the exterior angle theorem, Apply the triangle exterior angle theorem. See Example 2. The exterior angle theorem tells us that the measure of angle D is equal to the sum of angles A and B.In formula form: m