Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2021/paper-1/11/b/iii/solution

Put . Part (b)(ii) gives , so
The parameter increases strictly from to . Therefore the imaginary part increases from to , while the real part is . The endpoints are
The real axis crossing is at , giving at . The two imaginary axis crossings satisfy , giving
In order, the trajectory passes from its lower endpoint through , then the leftmost point , then , to its upper endpoint. It is a right-opening parabola segment, traversed continuously upward as shown in the right panel.

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