I would interpret this as saying that the center is at (21/2, 21/2) and the radius is 21/2- 1= 19/2 or 20- 21/2= 19/2.

Or are you saying that the center is at (1, 1) and (20,1) and (1, 20) are on the circle? In that case the radius is 19 units.

So? You didn't say that X was a point on the circle. Did you intend that?now place an X in position 12,6

now determine the diagonal distance :

d = sqrt ( (12-1)*(12-1) + (6-20)*(6-20) )

d = sqrt ( 317 )

d = 18 (rounded)

but X is 19 diagonal units?

Why is that wrong? What are you trying to do?Try another :

place an X in position 10,11

d = sqrt ( (10-1)*(10-1) + ( 11-20)*(11-20) )

d = sqrt (162)

d = 13 (rounded) this is correct

Try another one for a wrong answer:

place an X in position 19,20

d = sqrt ( (19-1)*(19-1) + (20-20)*(20-20) )

d = sqrt (324)

d = 18

I lost and have been doing the math all day and do not see where I am making a cock up!

Help please?

Thanks