##11 pi## radians

The smallest polygon is the triangle. It has a total of ##pi## radians as the sum of internal angles. Any other polygon can be decomposed as many triangles as ##n-2## with ##n## the number of sides. So the sum of interior angles for a polygon ##n## sided is given by

##(n-2)pi## for ##n > 3##. The ##13##-sided polygon has an interior sum of angles equal to ##11 pi## radians