prep for 2023. Fixed many bugs. Added pdf guide

vendor/markbaker/complex/classes/src/functions/acosh.php

@@ -0,0 +1,34 @@
+<?php
+
+/**
+ *
+ * Function code for the complex acosh() 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 hyperbolic cosine of a complex number.
+ *
+ * @param     Complex|mixed    $complex    Complex number or a numeric value.
+ * @return    Complex          The inverse hyperbolic cosine of the complex argument.
+ * @throws    Exception        If argument isn't a valid real or complex number.
+ */
+function acosh($complex)
+{
+    $complex = Complex::validateComplexArgument($complex);
+
+    if ($complex->isReal() && ($complex->getReal() > 1)) {
+        return new Complex(\acosh($complex->getReal()));
+    }
+
+    $acosh = acos($complex)
+        ->reverse();
+    if ($acosh->getReal() < 0.0) {
+        $acosh = $acosh->invertReal();
+    }
+
+    return $acosh;
+}