Solution

ID: past-exam-of-the-algebra-analysis-and-differential-equations-1-course-of-the-university-of-oxford/2009/4/ii/solution

The modulus map is continuous, the denominator is positive everywhere, and sums, products and quotients with nonzero denominator preserve continuity. Hence is continuous throughout .
For , , so as . The chosen argument is continuous locally away from the negative real axis, making continuous there as well. At a point , , approach along . From , ; from , . The value assigned on the cut is . Thus is discontinuous at every strictly negative real point, and therefore is not a continuous map on the entire complex plane. Its radial factor is , as printed, rather than the of a square root.

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