1 | initial version |

You can find out what you're dealing with by looking at the object's parent:

```
sage: my_E = E([0,1,1]); my_E
((-t + 1)/(-q*t + 1))*x0*x1 + ((-t + 1)/(-q*t + 1))*x0*x2 + x1*x2
sage: my_E.parent()
Multivariate Polynomial Ring in x0, x1, x2 over Fraction Field of Multivariate Polynomial Ring in q, t over Rational Field
```

So you can read about multivariate polynomials in the reference manual. In this case you can do

```
sage: q, t = my_E.parent().base_ring().gens()
sage: my_E.map_coefficients(lambda c: c.subs({t : 0}))
x0*x1 + x0*x2 + x1*x2
```

This last polynomial still belongs to the same ring as `my_E`

, but you could change that using the `change_ring()`

method if you want. You can also get at the `x`

's:

```
sage: x = my_E.parent().gens()
sage: x[0]
x0
sage: my_E.subs({x[0] : 0})
x1*x2
```

Alternatively you can convert the whole thing into the symbolic ring:

```
sage: var('t')
sage: SR(my_E).subs(t=0)
x0*x1 + x0*x2 + x1*x2
```

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.