Equation of Circle
Form 1
\((x - a)^2 + (y - b)^2 = R^2\)
Centre = \((a, b)\)
Radius = \(R\)
Form 2
\(x^2 + y^2 + Ax + By + C = 0\)
Centre = \(\left(- \dfrac 12 A, \: - \dfrac 12 B \right)\)
Radius = \(\sqrt{\dfrac 14 A^2 + \dfrac 14 B^2 - C}\)
Tangent of Circle
Tangent of circle is perpendicular to radius.
Exercise