Draw a diagram to show the circle and the tangent at the point (2, 4) labelling this P. Draw the radius from the centre of the circle to P. The tangent will have an equation in the form \(y = mx + c\) ...

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 \(\sqrt 7\).