1. By definition, when you add the exterior angles of a regular polygon, you obtain 360 degrees and the number of sides of that polygon can be calculated by dividing 360 degrees by the measure of the exterior angle of it.
2. As you know, the number of sides cannot be fractions, therefore, if you make the folllowing division:
360°/50°=36/5
You obtain a fraction.
3. Then, an exterior angle of a regular polygon cannot have the measure is 50°.
