acos.php
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<?php
/**
*
* Function code for the complex acos() function
*
* @copyright Copyright (c) 2013-2018 Mark Baker (https://github.com/MarkBaker/PHPComplex)
* @license https://opensource.org/licenses/MIT MIT
*/
namespace Complex;
/**
* Returns the inverse cosine of a complex number.
*
* @param Complex|mixed $complex Complex number or a numeric value.
* @return Complex The inverse cosine of the complex argument.
* @throws Exception If argument isn't a valid real or complex number.
*/
function acos($complex)
{
$complex = Complex::validateComplexArgument($complex);
$square = clone $complex;
$square = multiply($square, $complex);
$invsqrt = new Complex(1.0);
$invsqrt = subtract($invsqrt, $square);
$invsqrt = sqrt($invsqrt);
$adjust = new Complex(
$complex->getReal() - $invsqrt->getImaginary(),
$complex->getImaginary() + $invsqrt->getReal()
);
$log = ln($adjust);
return new Complex(
$log->getImaginary(),
-1 * $log->getReal()
);
}