# Function derivative #

Takes the derivative of an expression expressed in parser Nodes. The derivative will be taken over the supplied variable in the second parameter. If there are multiple variables in the expression, it will return a partial derivative.

This uses rules of differentiation which can be found here:

## Syntax #

``````derivative(expr, variable)
derivative(expr, variable, options)
``````

### Parameters #

Parameter Type Description
`expr` Node | string The expression to differentiate
`variable` SymbolNode | string The variable over which to differentiate
`options` {simplify: boolean} There is one option available, `simplify`, which is true by default. When false, output will not be simplified.

### Returns #

Type Description
ConstantNode | SymbolNode | ParenthesisNode | FunctionNode | OperatorNode The derivative of `expr`

## Examples #

``````math.derivative('x^2', 'x')                     // Node {2 * x}
math.derivative('x^2', 'x', {simplify: false})  // Node {2 * 1 * x ^ (2 - 1)
math.derivative('sin(2x)', 'x'))                // Node {2 * cos(2 * x)}
math.derivative('2*x', 'x').eval()              // number 2
math.derivative('x^2', 'x').eval({x: 4})        // number 8
const f = math.parse('x^2')
const x = math.parse('x')
math.derivative(f, x)                           // Node {2 * x}
``````