Chi 函数定义如下
C h i ( z ) = ∫ 0 z cosh ( t ) t d t {\displaystyle {\it {Chi}}\left(z\right)=\int _{0}^{z}\!{\frac {\cosh \left(t\right)}{t}}{dt}}
C h i ( z ) {\displaystyle Chi(z)} 是下列三阶非线性常微分方程的一个解:
z d d z w ( z ) − 2 d 2 d z 2 w ( z ) − z d 3 d z 3 w ( z ) = 0 {\displaystyle z{\frac {d}{dz}}w\left(z\right)-2\,{\frac {d^{2}}{d{z}^{2}}}w\left(z\right)-z{\frac {d^{3}}{d{z}^{3}}}w\left(z\right)=0}
即:
w ( z ) = _ C 1 + _ C 2 C h i ( z ) + _ C 3 S h i ( z ) {\displaystyle w\left(z\right)={\it {\_C1}}+{\it {\_C2}}\,{\it {Chi}}\left(z\right)+{\it {\_C3}}\,{\it {Shi}}\left(z\right)}
C h i ( − z ) = C h i ( z ) {\displaystyle Chi(-z)=Chi(z)}
Meijer G函数
超几何函数