let the equation of aline be x+y+2. If the co ordinates of orthocenter and circum center are(1,1) and (2,0)then the radius of circumcircle is

I fjust this much information is given, assuming the question to be complete,
Proceed with calculating the coordinates of length and foot of perpendicular from both the points on the line.As the circumcenter would meet the line at the point of bisection of the side contained in the line whose eqn is given, find the eqn of circumcircle and the line passing through the orthocenter and perpendicular to the line. This is the eqn of the altitude on which the vertex would lie. Also, the circumcircle whose eqn has been formed will also pass through the vertices. So, the point of intersection would give the coordinates of the vertex opposite ti the side which is contained in the line whose eqn is given.

For finding the radius of circumcircle, you will need either a vertex or a side more.
So, I guess the question is incomplete.

So, all the best.