PHP deg2rad() Function

The deg2rad() function in PHP converts angles from degrees to radians. This function is essential when working with trigonometric functions like sin(), cos(), and tan(), which require angle arguments in radians rather than degrees.

Syntax

deg2rad(float $number) : float

Parameters

Return Value

Returns a float number representing the angle in radians. The conversion follows the formula: radians = degrees × ?/180.

Example

Here's how to convert degrees to radians using deg2rad() −

<?php
    $degrees = 45;
    $radians = deg2rad($degrees);
    echo "deg2rad(" . $degrees . ") = " . $radians . "
";
    
    // Common angle conversions
    echo "30 degrees = " . deg2rad(30) . " radians
";
    echo "90 degrees = " . deg2rad(90) . " radians
";
    echo "180 degrees = " . deg2rad(180) . " radians
";
?>

deg2rad(45) = 0.78539816339745
30 degrees = 0.52359877559830 radians
90 degrees = 1.5707963267949 radians
180 degrees = 3.1415926535898 radians

Practical Application

The function is commonly used with trigonometric calculations −

<?php
    $angle_degrees = 60;
    $angle_radians = deg2rad($angle_degrees);
    
    echo "Angle: " . $angle_degrees . " degrees
";
    echo "Sin(" . $angle_degrees . "°) = " . sin($angle_radians) . "
";
    echo "Cos(" . $angle_degrees . "°) = " . cos($angle_radians) . "
";
    echo "Tan(" . $angle_degrees . "°) = " . tan($angle_radians) . "
";
?>

Angle: 60 degrees
Sin(60°) = 0.86602540378444
Cos(60°) = 0.5
Tan(60°) = 1.7320508075689

Conclusion

The deg2rad() function is essential for mathematical calculations involving trigonometry. Use it whenever you need to convert degree measurements to radians for PHP's trigonometric functions.