功能: 计算Bulirsch第2类不完全椭圆积分
格式: EllipticBulirschEl2(x, kc, a, b)
x  : 数值或者矩阵变量
kc : 数值或者矩阵变量
a  : 数值或者矩阵变量
b  : 数值或者矩阵变量

说明:
1、函数定义如下
$$
\begin{aligned}
\mathbf{EllipticBulirschEl2}(x, k_c, a, b) &= \int_0^{\arctan(x)} \dfrac{a+b\tan^2(t)}{\sqrt{(1+\tan^2(t))(1+k_c^2\tan^2(t))}}dt
\\
&=\int_0^x\dfrac{a+bt^2}{(1+t^2)\sqrt{(1+t^2)(1+k_c^2t^2)}}dt
\end{aligned}
$$
参考:
[1] Bulirsch R. An extension of the Bartky-transformation to incomplete elliptic integrals of the third kind[J]. Numerische Mathematik, 1969, 13(3): 266-284.
[2] Carlson B C. Numerical computation of real or complex elliptic integrals[J]. Numerical Algorithms, 1995, 10(1): 13-26.
[3] NIST handbook of mathematical functions hardback and CD-ROM[M]. Cambridge university press, 2010.

例子:
a = EllipticBulirschEl2(1,2,3,4)//执行得到如下结果
a =
[ 2.06227711264535 ]