19: Symmetry: Since y is an odd function and x is even, the graph is symmetric about the x-axis. Both functions are 2π-periodic, so from now on only t from [0,2π] will be considered.
Intercepts: (0,0) for t = π/2 and t = 3π/2; (1,0) for t = 0 and t = 2π; (−1,0) for t = π.

Limits: There are no open-ended endpoints for t, so no limits are necessary.
Picture:

Next investigate directions in which the curve goes and mononoticity of the resulting graph, inclusing "interesting" points.

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Answer