Si 函数 定义如下[1] [2]
Si(x)的二维图像
S
i
(
z
)
=
∫
0
z
sin
(
t
)
t
d
t
{\displaystyle {\it {Si}}\left(z\right)=\int _{0}^{z}\!{\frac {\sin \left(t\right)}{t}}{dt}}
S
i
(
z
)
{\displaystyle Si(z)}
S
i
(
z
)
=
z
d
d
z
w
(
z
)
+
2
d
2
d
z
2
w
(
z
)
+
z
d
3
d
z
3
w
(
z
)
=
0
{\displaystyle {\it {Si}}\left(z\right)=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
S
i
(
z
)
+
_
C
3
C
i
(
z
)
{\displaystyle w\left(z\right)={\it {\_C1}}+{\it {\_C2}}\,{\it {Si}}\left(z\right)+{\it {\_C3}}\,{\it {Ci}}\left(z\right)}
表示为其他特殊函数
编辑
Meijer G函数
{\displaystyle }
−
1
2
π
G
1
,
3
1
,
1
(
1
/
4
z
2
|
1
/
2
,
0
,
0
1
)
{\displaystyle {\frac {-1}{2}}\,{\sqrt {\pi }}G_{1,3}^{1,1}\left(1/4\,{z}^{2}\,{\Big \vert }\,_{1/2,0,0}^{1}\right)}
超几何函数
S
i
(
z
)
=
z
∗
1
F
2
(
1
/
2
;
3
/
2
,
3
/
2
;
−
(
1
/
4
)
∗
z
2
)
{\displaystyle Si(z)=z*_{1}F_{2}(1/2;3/2,3/2;-(1/4)*z^{2})}
级数展开
编辑
S
i
(
z
)
=
(
z
−
1
18
z
3
+
1
600
z
5
−
1
35280
z
7
+
1
3265920
z
9
−
1
439084800
z
11
+
1
80951270400
z
13
+
O
(
z
15
)
)
{\displaystyle {\it {Si}}\left(z\right)=(z-{\frac {1}{18}}{z}^{3}+{\frac {1}{600}}{z}^{5}-{\frac {1}{35280}}{z}^{7}+{\frac {1}{3265920}}{z}^{9}-{\frac {1}{439084800}}{z}^{11}+{\frac {1}{80951270400}}{z}^{13}+O\left({z}^{15}\right))}
帕德近似
编辑
S
i
(
z
)
≈
(
−
33317056220720070437
9686419676455776844590000
z
7
+
67177799936189717
98024149196718942600
z
5
−
540705278447237
16111793096107650
z
3
+
z
)
(
1
+
177197169001594
8055896548053825
z
2
+
87368534024947
363052404432292380
z
4
+
212787117226481
131788022808922133940
z
6
+
10065927082366801
1707972775603630855862400
z
8
)
−
1
{\displaystyle Si(z)\approx \left(-{\frac {33317056220720070437}{9686419676455776844590000}}\,{z}^{7}+{\frac {67177799936189717}{98024149196718942600}}\,{z}^{5}-{\frac {540705278447237}{16111793096107650}}\,{z}^{3}+z\right)\left(1+{\frac {177197169001594}{8055896548053825}}\,{z}^{2}+{\frac {87368534024947}{363052404432292380}}\,{z}^{4}+{\frac {212787117226481}{131788022808922133940}}\,{z}^{6}+{\frac {10065927082366801}{1707972775603630855862400}}\,{z}^{8}\right)^{-1}}
Si(x) Re complex 3D plot Si(x) Im complex 3D plot Si(x) abs complex 3D plot
Si(x) abs complex density plot Si(x) Re complex density plot Si(x) Im complex density plot
参考文献
编辑
^ Abramowitz, M. and Stegun, I. A. (Eds.). "Sine and Cosine Integrals." §5.2 inHandbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, 9th printing. New York: Dover, pp. 231-233, 1972.
^
Sloane, N. J. A. Sequence A061079 in "The On-Line Encyclopedia of Integer Sequences
_2D_plot.png)
_Re_complex_3D_plot.png)
_Im_complex_3D_plot.png)
_abs_complex_3D_plot.png)
_abs_complex_density_plot.JPG)
_Re_complex_density_plot.JPG)
_Im_complex_density_plot.JPG)