The lines with equations y=12x\displaystyle y = \frac{1}{2}xy=21x and y=−12x\displaystyle y = -\frac{1}{2}xy=−21x are tangents to a circle at (4,2)(4, 2)(4,2) and (4,−2)(4, -2)(4,−2) respectively.
Find the coordinates of the centre of the circle.
Hence find an equation for the circle.
292 exam-style questions on Edexcel A Level Maths Circles, covering 6.1 Midpoints and Perpendicular Bisectors, 6.2 Equation of a Circle, 6.3 Intersections of Straight Lines and Circles, 6.4 Use Tangent and Chord Properties, and 6.5 Circles and Triangles. Each one has a worked solution and a mark scheme showing where the marks go.