# Inv romberg

From WeBWorK

### inv_romberg

**Syntax**

`$right_hand_endpoint = inv_romberg($rf_func, $left_hand_endpoint, $value) ; `

**Params**

`$rf_func`

refers to a subroutine of one variable defining the function.`$left_hand_endpoint`

is the left hand endpoint of the integral.`$value`

is the desired value for the integral.

**Returns**

A number representing the right hand endpoint of the interval whose definite integral has the desired value.

**Examples**

`$b = inv_romberg(sub { my $x=shift; (1/sqrt($PI) )*exp(-$x**2); }, 0, 1/4);`

# find the upper limit b so that the area under the normal distribution on the inteval between 0 and b is 1/4.

**Notes**

Can be used, for example, to find intervals under a normal distribution curve that have a desired value. Used in many statistics problems.