prep for 2023. Fixed many bugs. Added pdf guide

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

@@ -0,0 +1,40 @@
+<?php
+
+/**
+ *
+ * Function code for the complex tan() function
+ *
+ * @copyright  Copyright (c) 2013-2018 Mark Baker (https://github.com/MarkBaker/PHPComplex)
+ * @license    https://opensource.org/licenses/MIT    MIT
+ */
+namespace Complex;
+
+/**
+ * Returns the tangent of a complex number.
+ *
+ * @param     Complex|mixed    $complex    Complex number or a numeric value.
+ * @return    Complex          The tangent of the complex argument.
+ * @throws    Exception        If argument isn't a valid real or complex number.
+ * @throws    \InvalidArgumentException    If function would result in a division by zero
+ */
+function tan($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()
+    );
+}