# 3.5.1.3.60 Y1

## Description

This function returns the first order Bessel function of the second kind and has the following form:

Y1(x)

The formula for the equation is:

$Y_1(x)=\lim_{v \rightarrow 1} Y_1(v, 1)$

where

$Y_1(v,1)=\frac{J_{1}(x,v)\cos(v\pi)-J_{1}(x,-v)}{sin(v\pi)}$

## Syntax

double y1(double x)

## Parameter

x

the input parameter.

## Return

Returns the first order Bessel function of second kind at x.

## Example

aa = y1(5);
aa = ; //0.14786314339123