What is atan() in PHP?

The atan() functionalso called the arc tangent function returns the inverse tangent of a number. To be more specific, atan() returns the inverse tangent of a number in radians.

This means that tan(atan(x)) would be equal to x.

Figure 1 shows the mathematical representation of the atan() function.

Figure 1: Mathematical representation of inverse tangent function

To convert radians to degrees, use:

degrees = radians * ( 180.0 / M_PI )

Below is the graphical representation of the atan function.

Graphical representation of atan() function
Graphical representation of atan() function

Syntax

float atan(num)

Parameter

This function requires a number as a parameter.

Return value

atan() will return the inverse tangent of a number (in radians) that is sent as a parameter. The return value lies within [-pi/2,pi/2] radians.

Example

<?php
#Positive number in radians
echo("atan(0.5): ");
echo (atan(0.5));
echo(" Radians")
?>	
<?php
#Negative number in radians
echo("atan(-0.5): ");
echo (atan(-0.5));
echo(" Radians")
?>
<?php
#tan(atan(x))
echo("tan(atan(0.5)): ");
echo (tan(atan(0.5)));
echo(" Radians")
?>
<?php
#applying atan() and then converting the result in radians to degrees
#radians = 1
echo("atan(1) * (180.0 / M_PI)): ");
echo (atan(1) * (180.0 / M_PI));
echo(" Degrees")
?>

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