Challenging Questions

Mathematics – Compulsory Part

Learning Unit: Equations of circles

Question M0-13-08

A point \(P \, (x_1, y_1)\) lies on a circle \(C: x^2 + y^2 + Dx + Ey + F = 0\). Show that the tangent to \(C\) at \(P\) is given by

\( x_1x + y_1y + \frac{D}{2}(x_1 + x) + \frac{E}{2}(y_1 + y) + F = 0 \)

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