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diff --git a/vendor/markbaker/complex/classes/src/functions/acos.php b/vendor/markbaker/complex/classes/src/functions/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 $complex Complex number or a numeric value.
+ * @return Complex The inverse cosine of the complex argument.
+ * @throws Exception If argument isn't a valid real or complex number.
+ */
+if (!function_exists(__NAMESPACE__ . '\\acos')) {
+ function acos($complex): 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()
+ );
+ }
+}