Let $S$ be the union of the set of all points inside a regular nonagon with side length $2$ units and the set of all points less than $1$ unit away from an arbitrary point on the perimeter of the nonagon. What, in units, is the perimeter of $S$?
check out CPhill's answer here:
https://web2.0calc.com/questions/funky-circle-areas
i hope CPhill's solution helped you! if you have any follow-up questions, feel free to ask! :)