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<html><head><title>XLISP acos</title>
<link rel="stylesheet" type="text/css" href="reference.css">
</head>
<body>
<a href="../start.htm">Nyquist / XLISP 2.0</a> -
<a href="../manual/contents.htm">Contents</a> |
<a href="../tutorials/tutorials.htm">Tutorials</a> |
<a href="../examples/examples.htm">Examples</a> |
<a href="reference-index.htm">Reference</a>
<hr>
<h1>acos</h1>
<hr>
<p><table cellpadding="0" cellspacing="0" style="margin-left:10px"><tbody>
<tr valign="top">
<td><nobr>Type:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>Lisp function (closure)</nobr></td>
</tr>
<tr valign="top">
<td><nobr>Source:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr></nobr></td>
</tr>
</tbody></table></p>
<h2>Syntax</h2>
<p><div class="box">
<dl>
<dt><nobr>(<b>acos</b> <i>flonum</i>)</nobr></dt>
<dd><i>flonum</i> - an integer or floating point expression<br>
returns - the <nobr>arc-cosine</nobr> of the number</dd>
</dl>
</div></p>
<p><b>Note:</b> the 'acos' function is not implemented in Nyquist. Here
is a Lisp implementation of 'acos', using the <a href="atan.htm">atan</a>
function:</p>
<pre class="example">
(defun <font color="#0000CC">acos</font> (x)
(cond ((not (numberp x)) (error <font color="#880000">"bad argument type"</font> x))
((= x 1) 0.0)
((= x -1) pi)
((< -1 x 1) (+ (atan (/ (- x) (sqrt (1+ (* x (- (float x))))))) (/ pi 2.0)))
(t (error <font color="#880000">"argument out of range"</font> x))))
</pre>
<h2>Description</h2>
<p>The 'acos' function returns the <nobr>arc-cosine</nobr> of an integer or
floating point expression. <nobr>The result</nobr> is a floating point
number in radians. <nobr>If the</nobr> argument is less <nobr>than -1</nobr>
or greater <nobr>than +1</nobr>, the <nobr>arc-cosine</nobr> is a complex
number. Complex numbers are not available <nobr>in XLISP</nobr>. <nobr>In
this</nobr> case the 'acos' function signals an 'argument out of range'
error.</p>
<h2>Examples</h2>
<pre class="example">
(acos 0.0) => 1.5708
(acos 1.0) => 0.0
(acos -1.0) => 3.14159
</pre>
<p>See also:</p>
<ul>
<li><nobr>Contents → <a href="../manual/contents.htm#arithmetic-functions">Arithmetic Functions</a></nobr></li>
</ul>
<p><nobr> <a href="#top">Back to Top</nobr></a></p>
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<a href="../start.htm">Nyquist / XLISP 2.0</a> -
<a href="../manual/contents.htm">Contents</a> |
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