Which expression is equivalent to is Measure of angle 4? A triangle has angles 1, 2, 3. The exterior angle to angle 1 is 4, to angle 2 is 5, to angle 3 is 6. Measure of angle 2 measure of angle 3 Measure of angle 1 measure of angle 2 Measure of angle 1 measure of angle 3 Measure of angle 5 measure of angle 6.