tan.php

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<?php

namespace Complex;

if (!function_exists(__NAMESPACE__ . '\\tan')) {
    function tan($complex): Complex
    {
        $complex = Complex::validateComplexArgument($complex);

        if ($complex->isReal()) {
            return new Complex(\tan($complex->getReal()));
        }

        $real = $complex->getReal();
        $imaginary = $complex->getImaginary();
        $divisor = 1 + \pow(\tan($real), 2) * \pow(\tanh($imaginary), 2);
        if ($divisor == 0.0) {
            throw new \InvalidArgumentException('Division by zero');
        }

        return new Complex(
            \pow(sech($imaginary)->getReal(), 2) * \tan($real) / $divisor,
            \pow(sec($real)->getReal(), 2) * \tanh($imaginary) / $divisor,
            $complex->getSuffix()
        );
    }
}