how to do part ii

E Show that, if the line y= mx+c is a tangent to the ellipse E with equation 2 = 1, then c2 = 62 + arm. E The locus of points at which two perpendicular tangents to E meet is called its director curve. Use the result in part (i) to find a quadratic equation in m, with coefficients in terms of a, b, x and y, and hence show that the director curve of E is a circle, stating its centre and radius. (iii) Deduce the equation of the director curve of the circle with equation x2 + y =r2. E