             <span class="serif_italic">atan(x) = -π/2 - atan(1/x)</span>
                    </p></blockquote></div>
                  <p>
                    Substituting into the above we get:
                  </p>
                  <div class="blockquote"><blockquote class="blockquote"><p>
                      <span class="serif_italic">p = -atan(1/x) ; x &lt; 0</span>
                    </p></blockquote></div>
                  <p>
                    So the procedure is to calculate the cdf for -f