Math functions deg2rad() to convert Degree to Radian value in PHP

<?Php
echo deg2rad(0); // Output is 0
echo "<br>";
echo deg2rad(90); // Output  1.5707963267949
echo "<br>";
echo deg2rad(180); // Output is 3.1415926535898
echo "<br>";
echo deg2rad(270); // Output is 4.7123889803847 
?>

Syntax

deg2rad(X);

X is the number representing angular value in degree.

deg2rad() with round()

We can use round() to remove extra decimal places.

<?Php
echo round(deg2rad(90),2); // Output  is 1.57
?>

deg2rad() with sin() cos()

Decimal places Sin(), cos() and other trigonometric functions takes input in radian so while using if we are using data in degree then we have to convert them first and then use with Sin() , Cos() etc.

<?Php
echo sin(deg2rad(90)); // Output  is 1
?>

Let us try few more examples

<?Php
echo sin(deg2rad(0)); // Output  is 0
echo "<br>";
echo round(sin(deg2rad(180))); // Output  is 0
echo "<br>";
echo sin(deg2rad(270)); // Output  is -1
echo "<br>";
echo cos(deg2rad(0)); // Output  is 1
echo "<br>";
echo cos(deg2rad(180)); // Output  is -1
echo "<br>";
echo tan(deg2rad(45)); // Output  is 1
?>

Example: Calculating Radians for Trigonometric Functions

$degrees = 90;
$radians = deg2rad($degrees);
echo "Radians: " . $radians;  // Output: Radians: 1.5708
echo "Sine of 90 degrees: " . sin($radians);  // Output: 1

Example: Calculating Angular Velocity

$degrees_per_second = 30;
$radians_per_second = deg2rad($degrees_per_second);
echo "Radians per second: " . $radians_per_second;  // Output: 0.5236

Example: Using deg2rad() in the Haversine Formula

function haversine($lat1, $lon1, $lat2, $lon2) {
    $earth_radius = 6371;  // Radius of the Earth in km
    $dLat = deg2rad($lat2 - $lat1);
    $dLon = deg2rad($lon2 - $lon1);
    
    $a = sin($dLat/2) * sin($dLat/2) +
        cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * 
        sin($dLon/2) * sin($dLon/2);
    
    $c = 2 * atan2(sqrt($a), sqrt(1-$a));
    
    return $earth_radius * $c;  // Output in km
}

$distance = haversine(51.5074, -0.1278, 40.7128, -74.0060);  // London to New York
echo "Distance: " . $distance . " km";  // Output: Distance: 5570.22 km

Example: Converting an Array of Degrees to Radians

$angles = [0, 30, 45, 90, 180];
$radians = array_map('deg2rad', $angles);
print_r($radians);  // Output: Array ( [0] => 0 [1] => 0.5235987755983 [2] => 0.78539816339745 [3] => 1.5707963267949 [4] => 3.1415926535898 )

Plotting of SIN & COS curves by using PHP GD function with deg2rad()

Math Functions rad2deg() function

Subhendu Mohapatra

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deg2rad(): Convert Degree to Radian