Sech[2 z] == Sech[z]^2/(2 - Sech[z]^2)

Cell[BoxData[RowBox[List[RowBox[List["Sech", "[", RowBox[List["2", " ", "z"]], "]"]], "\[Equal]", FractionBox[SuperscriptBox[RowBox[List["Sech", "[", "z", "]"]], "2"], RowBox[List["2", "-", SuperscriptBox[RowBox[List["Sech", "[", "z", "]"]], "2"]]]]]]]]

<math xmlns='http://www.w3.org/1998/Math/MathML' mathematica:form='TraditionalForm' xmlns:mathematica='http://www.wolfram.com/XML/'> <semantics> <mrow> <mrow> <mi> sech </mi> <mo> &#8289; </mo> <mo> ( </mo> <mrow> <mn> 2 </mn> <mo> &#8290; </mo> <mi> z </mi> </mrow> <mo> ) </mo> </mrow> <mo> &#10869; </mo> <mfrac> <mrow> <msup> <mi> sech </mi> <mn> 2 </mn> </msup> <mo> ( </mo> <mi> z </mi> <mo> ) </mo> </mrow> <mrow> <mn> 2 </mn> <mo> - </mo> <mrow> <msup> <mi> sech </mi> <mn> 2 </mn> </msup> <mo> ( </mo> <mi> z </mi> <mo> ) </mo> </mrow> </mrow> </mfrac> </mrow> <annotation-xml encoding='MathML-Content'> <apply> <eq /> <apply> <sech /> <apply> <times /> <cn type='integer'> 2 </cn> <ci> z </ci> </apply> </apply> <apply> <times /> <apply> <power /> <apply> <sech /> <ci> z </ci> </apply> <cn type='integer'> 2 </cn> </apply> <apply> <power /> <apply> <plus /> <cn type='integer'> 2 </cn> <apply> <times /> <cn type='integer'> -1 </cn> <apply> <power /> <apply> <sech /> <ci> z </ci> </apply> <cn type='integer'> 2 </cn> </apply> </apply> </apply> <cn type='integer'> -1 </cn> </apply> </apply> </apply> </annotation-xml> </semantics> </math>

Cell[BoxData[RowBox[List[RowBox[List["HoldPattern", "[", RowBox[List["Sech", "[", RowBox[List["2", " ", "z_"]], "]"]], "]"]], "\[RuleDelayed]", FractionBox[SuperscriptBox[RowBox[List["Sech", "[", "z", "]"]], "2"], RowBox[List["2", "-", SuperscriptBox[RowBox[List["Sech", "[", "z", "]"]], "2"]]]]]]]]

2001-10-29