span>
<span class="keyword">double</span> <span class="identifier">sin_phi</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">sin</span><span class="special">(</span><span class="identifier">phi</span><span class="special">),</span> <span class="identifier">cos_phi</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cos</span><span class="special">(</span