Given that the regular polygon with 40 sides.
We need to determine the interior angle of the polygon.
Sum of the interior angle:
Sum of the interior angle can be determined using the formula,

where n is the number of side.
Substituting
in the above formula, we get;

Simplifying the values, we get;

Thus, the sum of the interior angles is 6840°
Measure of each interior angle:
The measure of each interior angle can be determined using the formula,

where n is the number of side.
Substituting
in the above formula, we get;

Simplifying the values, we get;

Dividing, we get,

Thus, the measure of each interior angle is 171°