This equation is the same as the general equation of a circle, it's just written in a different form. Example Find the equation of the circle with centre \((2, - 3)\) and radius \(\sqrt 7\).

We can use perpendicular gradients to find the value of \(m\), then use the coordinates of P to find the value of \(c\) in the equation. Example Find the equation of the tangent to the circle \(x ...