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

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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