 Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2001/paper-2/3/a/solution

x = ρ cos ϕ, y = ρ sin ϕ, z = z .

Here

ρ \geq 0

is the distance from the

z

axis and

ϕ

is measured around that axis. A full turn

ϕ \mapsto ϕ + 2 π

describes the same point.

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