Math Trigonometric functions acos() to get acos value of any radian as input in PHP

<?Php
echo acos(0); // Output is 1.5707963267949
echo "<br>";
echo acos(1); // Output  0
echo "<br>";
echo acos(-1); // Output is 3.1415926535898
echo "<br>";
echo acos(-5); // Output is NAN 
?>

Syntax

acos(X);

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

It takes input range from +1 to -1 , for any other input it returns NAN ( not a number ). How to check the output by using is_nan() ?

deg2rad() with acos()

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

<?Php
echo acos(deg2rad(0)); // 1.5707963267949
echo "<br>";
echo acos(deg2rad(90)); // NAN
echo "<br>";
echo acos(deg2rad(180)); // NAN 
?>

Example: Handling Out-of-Range Values

$value = 2;  // Out of range
$result = acos($value);
if (is_nan($result)) {
    echo "Invalid input for acos";
}

Output

Invalid input for acos

Example: Calculating Angles in a Triangle Using Law of Cosines

$a = 5; $b = 6; $c = 7;
$angleC = acos(($a*$a + $b*$b - $c*$c) / (2 * $a * $b));
echo rad2deg($angleC);  // Output in degrees

Output

78.463040967185

Questions

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

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Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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acos(): the arc cosine (inverse cosine) of a given number in radians

deg2rad() with acos()

Example: Handling Out-of-Range Values

Example: Calculating Angles in a Triangle Using Law of Cosines

Questions

Subhendu Mohapatra