You need both a point and the gradient to find its equation. You are usually given the point - it's where the tangent meets the circle. To find the gradient use the fact that the tangent is ...

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. Find the equation of the tangent to the circle \(x^2 + y^2 ...