I didn't know what the circumcenter is, so I went and looked it up.
In the process, I accidentally learned something. Thank you.
The circumcenter of a right triangle is the point where
the perpendicular bisectors of all three sides meet.
For the triangle on your screen, that point is the mid-point of the
hypotenuse. It looks like (-5/2, -2).
I attached my drawing to this answer.
Please have a look.
