I can easily use parametric_plot() to plot 1 parametric function at once. For example

```
parametric_plot((sin(2*t),cos(3*t)),(t,0.0,9),aspect_ratio=1)
```

plots a nice Lissajous curve.

I also can plot a circle:

```
parametric_plot((sin(t),cos(t)),(t,0.0,9),aspect_ratio=1)
```

But how can I plot both of them in a common coordinate system?

I tried:

```
parametric_plot([(sin(2*t),cos(3*t)),(sin(t),cos(t))],(t,0.0,9),aspect_ratio=1)
```

Which doesn't work -> Last error message: ''tuple' object is not callable'

I also tried:

```
pl1=parametric_plot((sin(t),cos(t)),(t,0.0,9),aspect_ratio=1)
pl2=parametric_plot((sin(2*t),cos(3*t)),(t,0.0,9),aspect_ratio=1)
pl1.add_primitive(pl2)
pl1
```

Error: 'Graphics' object has no attribute 'options'

Then how can I use parametric_plot() to plot two parametric functions at once, in a common coordinate system?