Where Should You Tether a Dog for Maximum Play Area?

[kalbert]

I am really not sure where to even start with this question, at which point, (A,B,C) would the dog have a maximum area to play if tethered by a 20ft leash?

 

[SteamKing]

If the dog's leash is tied at point A, for example, how much area could be swept out by a 20-ft leash? What shape does the area have? Rinse and repeat for the other points indicated.

 

[Mentallic]

I am really not sure where to even start with this question, at which point, (A,B,C) would the dog have a maximum area to play if tethered by a 20ft leash?

Since point A is in the middle of the upper wall, it's pretty obvious that the furthest distance from this point would be at either corner on the bottom wall. Can you find the distance from A to either of those corners?