pan> <span class="mi">2</span> <span class="o">*</span> <span class="n">pi</span> <span class="o">*</span> <span class="n">nu</span> <span class="o">*</span> <span class="p">(</span><span class="n">t</span> <span class="o">-</span> <span class="n">t_origin</span><span class="p">))</span>
    <span class="o">*</span> <span class="n">sp</span><span class="o">.</span><span class="n">exp</span><span class="p">(</span><span class="o">-</span><span class="n">R</span> <span class="o">*</span> <span class="n">sp</s