Goat Tethered to Silo

What is the area of the region a goat tethered to a silo can graze? Let the radius of the silo be 1 unit. What is the length of the tether is pi? What if the length of the tether is 2*pi? What if the length of the tether is x?
Inspired by Doug Kuhlmann's very similar activity. This one allows you to change the length of the tether. Thanks Doug for all of your help over the years.
The following applet is intended to give some hints to get started with 2 different methods for calculating the area. Hint: it will require some calculus... likely stuff from the second half of Single Variable Calculus.