ass="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">tools</span><span class="special">;</span> <span class="comment">// For bracket_and_solve_root.</span>

   <span class="identifier">T</span> <span class="identifier">guess</span> <span class="special">=</span> <span class="identifier">sqrt</span><span class="special">(</span><span class="identifier">arc</span> <span cla