Math Trigonometric functions atan() to get arc tangent value of any radian as input in PHP

<?Php
echo atan(0); // Output is 0
echo "<br>";
echo atan(1); // Output  0.78539816339745
echo "<br>";
echo atan(-1); // -0.78539816339745
echo "<br>";
echo atan(4); // Output is 1.325817663668
echo "<br>";
echo atan(2); // Output is 1.1071487177941
echo "<br>";
echo atan(90); // Output is 1.5596856728973
?>

atan(X);

X is the angular value in radian. We get output as ARC tangent of the input angle.

deg2rad() with atan()

We can use deg2rad() to convert Degree value to radian and then use atan().

<?Php
echo atan(deg2rad(45)); // Output 0.66577375002835
echo "<br>";
echo atan(deg2rad(90)); // Output 1.0038848218539
echo "<br>";
echo atan(deg2rad(180)); // Output 1.2626272556789
echo "<br>";
echo atan(deg2rad(1)); // Output 0.017451520651466
echo "<br>";
echo atan(deg2rad(-1)); // Output -0.017451520651466
echo "<br>";
echo atan(deg2rad(-4)); // Output -0.069700080299613
echo "<br>";
echo atan(deg2rad(-90)); // Output -1.0038848218539
echo "<br>";
echo atan(deg2rad(-180)); // Output -1.2626272556789
?>

Example: Calculating Angle in a Triangle

$opposite = 5;
$adjacent = 10;
$angle = atan($opposite / $adjacent);  // Result in radians
$angle_in_degrees = rad2deg($angle);
echo $angle_in_degrees;  // Output: 26.565 degrees

Example: Handling Edge Cases

echo atan(0);  // Output: 0
echo atan(-1);  // Output: -0.785398163 (negative angle)

Example: Comparing atan() and atan2()

$y = 5;
$x = 10;
echo atan($y / $x);  // Output: 0.463 radians

// Using atan2 to handle full quadrant angles
echo atan2($y, $x);  // Output: 0.463 radians (same, but handles quadrant correctly)

Explanation:
Triangle Calculation: Demonstrates a practical application for calculating angles from side lengths.
Edge Case Handling: Explains what happens when input values are zero or negative.
Comparison: Clarifies when `atan()` or `atan2()` should be used for handling angles in different quadrants.

Questions

What does the `atan()` function in PHP do?
What is the purpose of the `atan()` function in PHP?
How is the `atan()` function used to calculate the arctangent (inverse tangent) of a number?
What is the range of values returned by the `atan()` function in PHP?
Can the `atan()` function be used with both degrees and radians?
What happens if you pass an invalid argument to the `atan()` function?
How can you use the `atan()` function to calculate the angle in radians given the tangent value?
Are there any alternative ways to calculate the inverse tangent in PHP besides using the `atan()` function?
Can the `atan()` function return a complex number?
What type of value does the `atan()` function return: integer, float, or something else?

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Subhendu Mohapatra

Author & Instructor at plus2net

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atan() : the arc tangent (inverse tangent) of a given number