1 | initial version |

I agree, it must be a problem with `normal`

. The following works as expected

sage: f(x,y)= x*y^3 sage: f (x, y) |--> x*y^3 sage: g = f.integral(y,0,7) sage: g (x, y) |--> 2401/4*x sage: plot(g,-5,5)

Where as this returns the error you've seen:

```
sage: f(x,y,z)= x*y^3+z
sage: g = f.integral(y,0,7)
sage: plot(g,-5,5)
...
ValueError: free variable: z
```

If you try to simply integrate the `normal`

function, do you get a number, or another function of `x`

?

Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.