Two circles of radius 4 are tangent to the graph of y^2 = 4x at the point (1, 2). ... I know how to find the tangent line from a circle and a given point, but ... 2a2=42. a2=8. a=±2√2. Then1−xc=±2√2 and 2−yc=±2√2. ... 4 from (1,2), so you could find these centers, and from there theequations of the circle