Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2012/ia/paper-1/1c/a/solution

Write with . In the complex plane, this is the vertical line through . The complex exponential gives , so its complex modulus is always . Conversely, every point of that modulus has an complex argument and is obtained in this way. The image is the entire circle centered at zero with radius , traversed repeatedly as varies; it is not a disk.
Figure 1.
The vertical line with real part one maps under the complex exponential to the circle of radius e
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