Returns the left-tailed Student's t-distribution.
| Name | Type | Description |
| arg1 | number | The numeric value at which to evaluate the distribution. |
| arg2 | number | An integer indicating the number of degrees of freedom that characterize the distribution. |
| arg3 | boolean | A logical value (true or false) that determines the function form. If it is true, the function returns the cumulative distribution function. If it is false, the function returns the probability density function. |