# Difference between revisions of "ATAN2"

Jump to navigation Jump to search

The _ATAN2 function returns the radian angle between the positive x-axis of a plane and the point given by the coordinates (x, y).

## Syntax

angle! = _ATAN2(y, x)

## Parameters

• y is the vertical axis position (row) as a positive, zero or negative floating point value.
• x is the horizontal axis position (column) as a positive, zero or negative floating point value.

## Description

• The DOUBLE radian angle returned is positive for upper row values where y > 0.
• _ATAN2(y, x) = ATN(y# / x#) when x > 0
• _ATAN2(y, x) = ATN(y# / x#) + _PI when x < 0
• _ATAN2(y, x) = _PI / 2 when x = 0
• The DOUBLE radian angle returned is 0 when x > 0 and _PI when x < 0 where y = 0
• The DOUBLE radian angle returned is negative for lower row values where y < 0.
• _ATAN2(y, x) = ATN(y# / x#) when x > 0
• _ATAN2(y, x) = ATN(y# / x#) - _PI when x < 0
• _ATAN2(y, x) = -_PI / 2 when x = 0
• _ATAN2(0, 0) is undefined and the function returns 0 instead of a division error.

### Errors

• With ATN(y / x), x can never be 0 as that would create a Division by Zero error 11 or #IND.

## See also

Navigation:
Keyword Reference - Alphabetical
Keyword Reference - By Usage
Main Wiki Page