# 2.4. Derivate¶

## 2.4.1. Example¶

derivate(formula, var)
Parameters: formula – The unevaluated formula var – The unevaluated derivation variable

Examples :

```\$ eq format "derivate( x^4 + sin(x^2) - ln(x) * exp(x) + 7, x )"
4      / 2\          x
d x  + sin\x / - ln(x).e  + 7
------------------------------
d x
```
```\$ eq eval "derivate( x^4 + sin(x^2) - ln(x) * exp(x) + 7, x )"
/  x            \
3          / 2\   | e            x|
4.x  + 2.x.cos\x / - |---- + ln(x).e |
\ x             /
```

You can force evaluation in formula and var.

## 2.4.2. Non-allowed derivations¶

Now it’s time to try a derivative with problems, by adding a non-variable inside it’s definition.

```\$ eq eval "derivate( x^4 + sin(x^2) - ln(x) * exp(x) + 7, x * x )"; true
Sorry your derivation doesn't have a good variable specification
4      / 2\          x
d x  + sin\x / - ln(x).e  + 7
------------------------------
d x.x

#
```

What you can see after the error text and the error expression, is the Eq’s favourite error value. <code>#</code> cannot be typed into expression, but it’s often generated to indicate error. If you find some, well, good luck :)