sub>v1,v2</sub>(x) = y * <a class="link" href="../../sf_beta/beta_derivative.html" title="Derivative of the Incomplete Beta Function">ibeta_derivative</a>(v2
                    / 2, v1 / 2, v2 / (v2 + v1 * x))
                  </p>
                  <p>
                    with y = (v2 * v1) / ((v2 + v1 * x) * (v2 + v1 * x))
                  </p>
                  <p>
                    and
                  </p>
                  <p>
                    f<sub>v1,v2</sub>(x) = y * <a class="link" href="