Triangle ABC has circumcenter O. If AB = 10 and the area of OAB is 30, find the circumradius of triangle ABC.
Circumradius = 2*30/10 = 6.
We can let A = (0,0)
And B = (10, 0)
Since [ OAB ] = 30....then we can let O be (5, 6)
The distance between O and any vertex is sqrt (5^2 + 6^2) = sqrt (61) = circumradius
So C must be ( 5, 6 + sqrt (61) )
See the image, here :
+312 
