Identify what is given
The problem will usually ask for an angle in a polygon, such as an interior angle, an exterior angle, or the total for all angles of a polygon. First determine whether the polygon is regular or not, and whether the question refers to one angle or the full set.
Use the angle relationships
For any polygon, an interior angle and its adjacent exterior angle form a straight line, so they add to 180°. If one is known, subtract from 180° to find the other.
For regular polygons
When all sides and angles are equal, divide the total angle measure evenly among the vertices. A useful check is that the exterior angles of any polygon add to 360°. So for a regular polygon with n sides, each exterior angle is 360°/n, and each interior angle is 180° - 360°/n.
Check your result
Make sure the angle measure is reasonable: an exterior angle should be less than 180°, and the interior angle should be less than 180° for a convex polygon. If you found both an interior and exterior angle at the same vertex, confirm they sum to 180°.
Simplify the final answer
Give the exact value or simplest form requested, and include units in degrees.
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