A regular nonagon is 9-sided polygon with all congruent sides and congruent interior angles.
The sum of exterior angles of n-sided polygon is 360°. If all interior angles of regular nonagon are congruent, then all exterior angles are congruent too.
Then each exterior angle has the measure of
[tex]\dfrac{360^{\circ}}{9}=40^{\circ}.[/tex]
Answer: [tex]40^{\circ}[/tex]
