1 | initial version |

Hi,

In Sage, the syntax `diff(g,x,m)`

where `x`

and `m`

are two symbolic variables, does not stand for the `m`

-th derivative of `g`

with respect to `x`

, but for the second order partial derivative of `g`

with one derivative taken with respect to `x`

and the other one with respect to `m`

, i.e. in LaTeX notation \frac{\partial^2 g}{\partial x \partial m}. This explains why example 1 returns 0 (`m`

does not appear in `g`

), while example 2 returns something nonzero (`(x^2-1)^n`

is a function of both `x`

and `n`

).

If, instead of a symbolic variable, the third argument of `diff`

is a non-negative integer `m`

, then the outcome is the `m`

-th derivative of `g`

with respect to `x`

: for instance

```
sage: g = x^2 + 3/2*(x^2 - 1)*x
sage: m = 3 # m is now an integer, not a symbolic variable
sage: diff(g, x, m)
9
```