p>atan(</samp><var>x</var><samp>)</samp></dt><dd class="col-md-8"> arc tangent function</dd>
<dt class="col-md-4"> <samp>atanh(</samp><var>x</var><samp>)</samp></dt><dd class="col-md-8"> inverse hyperbolic tangent function</dd>
<dt class="col-md-4"> <samp>atan2(</samp><var>y</var>,<var>x</var><samp>)</samp></dt><dd class="col-md-8"> arc tangent function of two variables</dd>
<dt class="col-md-4"> <samp>ceil(</samp><var>x</var><samp>)</samp></dt><dd class="col-md-8">smallest integral value not less than argu