# Perl Programming/Keywords/atan2

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`atan2` is the trigonometric function tangent that returns the arctangent of Y/X in the range -π to π.

```
atan2 Y, X
```

The code
prints the arc tangent in radians and degrees:

```
*PI = \3.1415926535;
$a = 3;
$b = 5;
$arctan = atan2($a, $b);
print "arctan(" . $a . ", " . $b . ") = " . $arctan . " rad = " . $arctan*180/$PI . " deg\n";
```

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