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 ExpIntegralEi

 http://functions.wolfram.com/06.35.26.0007.01

 Input Form

 ExpIntegralEi[z] == -Gamma[0, -z] + (1/2) (Log[z] - Log[1/z]) - Log[-z]

 Standard Form

 Cell[BoxData[RowBox[List[RowBox[List["ExpIntegralEi", "[", "z", "]"]], "\[Equal]", RowBox[List[RowBox[List["-", RowBox[List["Gamma", "[", RowBox[List["0", ",", RowBox[List["-", "z"]]]], "]"]]]], "+", RowBox[List[FractionBox["1", "2"], " ", RowBox[List["(", RowBox[List[RowBox[List["Log", "[", "z", "]"]], "-", RowBox[List["Log", "[", FractionBox["1", "z"], "]"]]]], ")"]]]], "-", RowBox[List["Log", "[", RowBox[List["-", "z"]], "]"]]]]]]]]

 MathML Form

 Ei ( z ) - Γ ( 0 , - z ) + 1 2 ( log ( z ) - log ( 1 z ) ) - log ( - z ) ExpIntegralEi z -1 Gamma 0 -1 z 1 2 z -1 1 z -1 -1 -1 z [/itex]

 Rule Form

 Cell[BoxData[RowBox[List[RowBox[List["HoldPattern", "[", RowBox[List["ExpIntegralEi", "[", "z_", "]"]], "]"]], "\[RuleDelayed]", RowBox[List[RowBox[List["-", RowBox[List["Gamma", "[", RowBox[List["0", ",", RowBox[List["-", "z"]]]], "]"]]]], "+", RowBox[List[FractionBox["1", "2"], " ", RowBox[List["(", RowBox[List[RowBox[List["Log", "[", "z", "]"]], "-", RowBox[List["Log", "[", FractionBox["1", "z"], "]"]]]], ")"]]]], "-", RowBox[List["Log", "[", RowBox[List["-", "z"]], "]"]]]]]]]]

 Date Added to functions.wolfram.com (modification date)

 2001-10-29