Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2004/paper-1/10/b/solution

The modulus equation says that has fixed distance eight from . Thus its locus is a circle of radius eight centered at , with Cartesian equation .
Figure 1.
The original circle, a horizontal stretch, a translation and a quarter-turn
. Original complex-plane loci. The map stretches only the horizontal coordinate; translates the circle; rotates that translated circle about the origin. Marked dots show each center. Details.

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