1 | initial version |

Try this:

```
someTriangle = parametric_plot3d(t*(1-s)*v + s*w, (t,0,1), (s,0,1))
```

In general, if you want `t`

to be in the interval `[a(s), b(s)]`

, just use `t' = a(s) + t*(b(s) - a(s))`

and let `t`

range from 0 to 1. For example, to graph the function `f(s,t) = 1`

for `s`

in `[0,1]`

and `t`

in `[s^2, s]`

:

```
sage: var('s,t')
(s, t)
sage: parametric_plot3d([s,(s^2 + t*(s - s^2)),1], (t,0,1), (s,0,1))
```

And here's a more complicated example:

```
sage: var('s,t,x,y')
(s, t, x, y)
sage: f = sin(x)*cos(y)
sage: tprime = s^2 + t*(s - s^2)
```

The rectangular plot:

```
sage: parametric_plot3d([s,t,f(x=s,y=t)], (t,0,1), (s,0,1))
```

Change coordinates to plot only a part of the t range:

```
sage: parametric_plot3d([s,tprime,f(x=s,y=tprime)], (t,0,1), (s,0,1))
```

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