1 | initial version |

It's because in `parametric_plot(f(t), (t, 0, 4*r + 2*pi*r))`

, the Python function `f`

is evaluated with the symbolic variable `t`

as an input, prior to giving any concrete value to `t`

:

```
sage: f(t)
(-4*pi + t - 8, -2)
```

To get the expected plot, you must split `f`

in two by defining

```
sage: def f0(x): return f(x)[0]
sage: def f1(x): return f(x)[1]
```

Then

```
sage: parametric_plot([f0, f1], (t, 0, 4*r + 2*pi*r))
```

gives the plot that you want.
Note that in the above command, one must write `[f0,f1]`

and not `[f0(t),f1(t)]`

: the latter would reproduce the incorrect behavior, by first evaluating `f0`

and `f1`

on the symbolic variable `t`

.

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