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 | | http://functions.wolfram.com/09.29.16.0056.01 | 
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 | | Sum[JacobiDN[z + (2 k EllipticK[m])/p, m]^2 
     (JacobiDN[z + (2 (k - 1) EllipticK[m])/p, m] + 
      JacobiDN[z + (2 (k + 1) EllipticK[m])/p, m]), {k, 0, p - 1}]/
   Sum[JacobiDN[z + (2 k EllipticK[m])/p, m], {k, 0, p - 1}] == 
  Sum[JacobiDN[(2 k EllipticK[m])/p, m]^2 
     (JacobiDN[(2 (k - 1) EllipticK[m])/p, m] + 
      JacobiDN[(2 (k + 1) EllipticK[m])/p, m]), {k, 0, p - 1}]/
   Sum[JacobiDN[(2 k EllipticK[m])/p, m], {k, 0, p - 1}] /; 
 Element[p, Integers] && p >= 2 | 
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 | | Cell[BoxData[RowBox[List[RowBox[List[RowBox[List[RowBox[List["(", RowBox[List[UnderoverscriptBox["\[Sum]", RowBox[List["k", "=", "0"]], RowBox[List["p", "-", "1"]]], RowBox[List[SuperscriptBox[RowBox[List["JacobiDN", "[", RowBox[List[RowBox[List["z", "+", FractionBox[RowBox[List["2", "k", " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"]]], ",", "m"]], "]"]], "2"], RowBox[List["(", RowBox[List[RowBox[List["JacobiDN", "[", RowBox[List[RowBox[List["z", "+", FractionBox[RowBox[List["2", RowBox[List["(", RowBox[List["k", "-", "1"]], ")"]], " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"]]], ",", "m"]], "]"]], "+", RowBox[List["JacobiDN", "[", RowBox[List[RowBox[List["z", "+", FractionBox[RowBox[List["2", RowBox[List["(", RowBox[List["k", "+", "1"]], ")"]], " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"]]], ",", "m"]], "]"]]]], ")"]]]]]], ")"]], "/", RowBox[List["(", RowBox[List[UnderoverscriptBox["\[Sum]", RowBox[List["k", "=", "0"]], RowBox[List["p", "-", "1"]]], RowBox[List["JacobiDN", "[", RowBox[List[RowBox[List["z", "+", FractionBox[RowBox[List["2", "k", " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"]]], ",", "m"]], "]"]]]], ")"]]]], "\[Equal]", RowBox[List[RowBox[List["(", RowBox[List[UnderoverscriptBox["\[Sum]", RowBox[List["k", "=", "0"]], RowBox[List["p", "-", "1"]]], RowBox[List[SuperscriptBox[RowBox[List["JacobiDN", "[", RowBox[List[FractionBox[RowBox[List["2", "k", " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"], ",", "m"]], "]"]], "2"], RowBox[List["(", RowBox[List[RowBox[List["JacobiDN", "[", RowBox[List[FractionBox[RowBox[List["2", RowBox[List["(", RowBox[List["k", "-", "1"]], ")"]], " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"], ",", "m"]], "]"]], "+", RowBox[List["JacobiDN", "[", RowBox[List[FractionBox[RowBox[List["2", RowBox[List["(", RowBox[List["k", "+", "1"]], ")"]], " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"], ",", "m"]], "]"]]]], ")"]]]]]], ")"]], "/", RowBox[List["(", RowBox[List[UnderoverscriptBox["\[Sum]", RowBox[List["k", "=", "0"]], RowBox[List["p", "-", "1"]]], RowBox[List["JacobiDN", "[", RowBox[List[FractionBox[RowBox[List["2", "k", " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"], ",", "m"]], "]"]]]], ")"]]]]]], "/;", RowBox[List[RowBox[List["p", "\[Element]", "Integers"]], "\[And]", RowBox[List["p", "\[GreaterEqual]", "2"]]]]]]]] | 
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   <math xmlns='http://www.w3.org/1998/Math/MathML' mathematica:form='TraditionalForm' xmlns:mathematica='http://www.wolfram.com/XML/'>  <semantics>  <mrow>  <mrow>  <mfrac>  <mrow>  <munderover>  <mo> ∑ </mo>  <mrow>  <mi> k </mi>  <mo> = </mo>  <mn> 0 </mn>  </mrow>  <mrow>  <mi> p </mi>  <mo> - </mo>  <mn> 1 </mn>  </mrow>  </munderover>  <mrow>  <msup>  <mrow>  <mi> dn </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mrow>  <mrow>  <mi> z </mi>  <mo> + </mo>  <mfrac>  <mrow>  <mn> 2 </mn>  <mo> ⁢ </mo>  <mi> k </mi>  <mo> ⁢ </mo>  <mrow>  <mi> K </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mi> m </mi>  <mo> ) </mo>  </mrow>  </mrow>  <mi> p </mi>  </mfrac>  </mrow>  <mo> ❘ </mo>  <mi> m </mi>  </mrow>  <mo> ) </mo>  </mrow>  <mn> 2 </mn>  </msup>  <mo> ⁢ </mo>  <mrow>  <mo> ( </mo>  <mrow>  <mrow>  <mi> dn </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mrow>  <mrow>  <mi> z </mi>  <mo> + </mo>  <mfrac>  <mrow>  <mn> 2 </mn>  <mo> ⁢ </mo>  <mrow>  <mo> ( </mo>  <mrow>  <mi> k </mi>  <mo> - </mo>  <mn> 1 </mn>  </mrow>  <mo> ) </mo>  </mrow>  <mo> ⁢ </mo>  <mrow>  <mi> K </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mi> m </mi>  <mo> ) </mo>  </mrow>  </mrow>  <mi> p </mi>  </mfrac>  </mrow>  <mo> ❘ </mo>  <mi> m </mi>  </mrow>  <mo> ) </mo>  </mrow>  <mo> + </mo>  <mrow>  <mi> dn </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mrow>  <mrow>  <mi> z </mi>  <mo> + </mo>  <mfrac>  <mrow>  <mn> 2 </mn>  <mo> ⁢ </mo>  <mrow>  <mo> ( </mo>  <mrow>  <mi> k </mi>  <mo> + </mo>  <mn> 1 </mn>  </mrow>  <mo> ) </mo>  </mrow>  <mo> ⁢ </mo>  <mrow>  <mi> K </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mi> m </mi>  <mo> ) </mo>  </mrow>  </mrow>  <mi> p </mi>  </mfrac>  </mrow>  <mo> ❘ </mo>  <mi> m </mi>  </mrow>  <mo> ) </mo>  </mrow>  </mrow>  <mo> ) </mo>  </mrow>  </mrow>  </mrow>  <mrow>  <munderover>  <mo> ∑ </mo>  <mrow>  <mi> k </mi>  <mo> = </mo>  <mn> 0 </mn>  </mrow>  <mrow>  <mi> p </mi>  <mo> - </mo>  <mn> 1 </mn>  </mrow>  </munderover>  <mrow>  <mi> dn </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mrow>  <mrow>  <mi> z </mi>  <mo> + </mo>  <mfrac>  <mrow>  <mn> 2 </mn>  <mo> ⁢ </mo>  <mi> k </mi>  <mo> ⁢ </mo>  <mrow>  <mi> K </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mi> m </mi>  <mo> ) </mo>  </mrow>  </mrow>  <mi> p </mi>  </mfrac>  </mrow>  <mo> ❘ </mo>  <mi> m </mi>  </mrow>  <mo> ) </mo>  </mrow>  </mrow>  </mfrac>  <mo> ⩵ </mo>  <mfrac>  <mrow>  <munderover>  <mo> ∑ </mo>  <mrow>  <mi> k </mi>  <mo> = </mo>  <mn> 0 </mn>  </mrow>  <mrow>  <mi> p </mi>  <mo> - </mo>  <mn> 1 </mn>  </mrow>  </munderover>  <mrow>  <msup>  <mrow>  <mi> dn </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mrow>  <mfrac>  <mrow>  <mn> 2 </mn>  <mo> ⁢ </mo>  <mi> k </mi>  <mo> ⁢ </mo>  <mrow>  <mi> K </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mi> m </mi>  <mo> ) </mo>  </mrow>  </mrow>  <mi> p </mi>  </mfrac>  <mo> ❘ </mo>  <mi> m </mi>  </mrow>  <mo> ) </mo>  </mrow>  <mn> 2 </mn>  </msup>  <mo> ⁢ </mo>  <mrow>  <mo> ( </mo>  <mrow>  <mrow>  <mi> dn </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mrow>  <mfrac>  <mrow>  <mn> 2 </mn>  <mo> ⁢ </mo>  <mrow>  <mo> ( </mo>  <mrow>  <mi> k </mi>  <mo> - </mo>  <mn> 1 </mn>  </mrow>  <mo> ) </mo>  </mrow>  <mo> ⁢ </mo>  <mrow>  <mi> K </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mi> m </mi>  <mo> ) </mo>  </mrow>  </mrow>  <mi> p </mi>  </mfrac>  <mo> ❘ </mo>  <mi> m </mi>  </mrow>  <mo> ) </mo>  </mrow>  <mo> + </mo>  <mrow>  <mi> dn </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mrow>  <mfrac>  <mrow>  <mn> 2 </mn>  <mo> ⁢ </mo>  <mrow>  <mo> ( </mo>  <mrow>  <mi> k </mi>  <mo> + </mo>  <mn> 1 </mn>  </mrow>  <mo> ) </mo>  </mrow>  <mo> ⁢ </mo>  <mrow>  <mi> K </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mi> m </mi>  <mo> ) </mo>  </mrow>  </mrow>  <mi> p </mi>  </mfrac>  <mo> ❘ </mo>  <mi> m </mi>  </mrow>  <mo> ) </mo>  </mrow>  </mrow>  <mo> ) </mo>  </mrow>  </mrow>  </mrow>  <mrow>  <munderover>  <mo> ∑ </mo>  <mrow>  <mi> k </mi>  <mo> = </mo>  <mn> 0 </mn>  </mrow>  <mrow>  <mi> p </mi>  <mo> - </mo>  <mn> 1 </mn>  </mrow>  </munderover>  <mrow>  <mi> dn </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mrow>  <mfrac>  <mrow>  <mn> 2 </mn>  <mo> ⁢ </mo>  <mi> k </mi>  <mo> ⁢ </mo>  <mrow>  <mi> K </mi>  <mo> ⁡ </mo>  <mo> ( </mo>  <mi> m </mi>  <mo> ) </mo>  </mrow>  </mrow>  <mi> p </mi>  </mfrac>  <mo> ❘ </mo>  <mi> m </mi>  </mrow>  <mo> ) </mo>  </mrow>  </mrow>  </mfrac>  </mrow>  <mo> /; </mo>  <mrow>  <mrow>  <mi> p </mi>  <mo> - </mo>  <mn> 2 </mn>  </mrow>  <mo> ∈ </mo>  <mi> ℕ </mi>  </mrow>  </mrow>  <annotation-xml encoding='MathML-Content'>  <apply>  <ci> Condition </ci>  <apply>  <eq />  <apply>  <times />  <apply>  <sum />  <bvar>  <ci> k </ci>  </bvar>  <lowlimit>  <cn type='integer'> 0 </cn>  </lowlimit>  <uplimit>  <apply>  <plus />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </uplimit>  <apply>  <times />  <apply>  <power />  <apply>  <ci> JacobiDN </ci>  <apply>  <plus />  <ci> z </ci>  <apply>  <times />  <cn type='integer'> 2 </cn>  <ci> k </ci>  <apply>  <ci> EllipticK </ci>  <ci> m </ci>  </apply>  <apply>  <power />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </apply>  </apply>  <ci> m </ci>  </apply>  <cn type='integer'> 2 </cn>  </apply>  <apply>  <plus />  <apply>  <ci> JacobiDN </ci>  <apply>  <plus />  <ci> z </ci>  <apply>  <times />  <cn type='integer'> 2 </cn>  <apply>  <plus />  <ci> k </ci>  <cn type='integer'> -1 </cn>  </apply>  <apply>  <ci> EllipticK </ci>  <ci> m </ci>  </apply>  <apply>  <power />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </apply>  </apply>  <ci> m </ci>  </apply>  <apply>  <ci> JacobiDN </ci>  <apply>  <plus />  <ci> z </ci>  <apply>  <times />  <cn type='integer'> 2 </cn>  <apply>  <plus />  <ci> k </ci>  <cn type='integer'> 1 </cn>  </apply>  <apply>  <ci> EllipticK </ci>  <ci> m </ci>  </apply>  <apply>  <power />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </apply>  </apply>  <ci> m </ci>  </apply>  </apply>  </apply>  </apply>  <apply>  <power />  <apply>  <sum />  <bvar>  <ci> k </ci>  </bvar>  <lowlimit>  <cn type='integer'> 0 </cn>  </lowlimit>  <uplimit>  <apply>  <plus />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </uplimit>  <apply>  <ci> JacobiDN </ci>  <apply>  <plus />  <ci> z </ci>  <apply>  <times />  <cn type='integer'> 2 </cn>  <ci> k </ci>  <apply>  <ci> EllipticK </ci>  <ci> m </ci>  </apply>  <apply>  <power />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </apply>  </apply>  <ci> m </ci>  </apply>  </apply>  <cn type='integer'> -1 </cn>  </apply>  </apply>  <apply>  <times />  <apply>  <sum />  <bvar>  <ci> k </ci>  </bvar>  <lowlimit>  <cn type='integer'> 0 </cn>  </lowlimit>  <uplimit>  <apply>  <plus />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </uplimit>  <apply>  <times />  <apply>  <power />  <apply>  <ci> JacobiDN </ci>  <apply>  <times />  <cn type='integer'> 2 </cn>  <ci> k </ci>  <apply>  <ci> EllipticK </ci>  <ci> m </ci>  </apply>  <apply>  <power />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </apply>  <ci> m </ci>  </apply>  <cn type='integer'> 2 </cn>  </apply>  <apply>  <plus />  <apply>  <ci> JacobiDN </ci>  <apply>  <times />  <cn type='integer'> 2 </cn>  <apply>  <plus />  <ci> k </ci>  <cn type='integer'> -1 </cn>  </apply>  <apply>  <ci> EllipticK </ci>  <ci> m </ci>  </apply>  <apply>  <power />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </apply>  <ci> m </ci>  </apply>  <apply>  <ci> JacobiDN </ci>  <apply>  <times />  <cn type='integer'> 2 </cn>  <apply>  <plus />  <ci> k </ci>  <cn type='integer'> 1 </cn>  </apply>  <apply>  <ci> EllipticK </ci>  <ci> m </ci>  </apply>  <apply>  <power />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </apply>  <ci> m </ci>  </apply>  </apply>  </apply>  </apply>  <apply>  <power />  <apply>  <sum />  <bvar>  <ci> k </ci>  </bvar>  <lowlimit>  <cn type='integer'> 0 </cn>  </lowlimit>  <uplimit>  <apply>  <plus />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </uplimit>  <apply>  <ci> JacobiDN </ci>  <apply>  <times />  <cn type='integer'> 2 </cn>  <ci> k </ci>  <apply>  <ci> EllipticK </ci>  <ci> m </ci>  </apply>  <apply>  <power />  <ci> p </ci>  <cn type='integer'> -1 </cn>  </apply>  </apply>  <ci> m </ci>  </apply>  </apply>  <cn type='integer'> -1 </cn>  </apply>  </apply>  </apply>  <apply>  <in />  <apply>  <plus />  <ci> p </ci>  <cn type='integer'> -2 </cn>  </apply>  <ci> ℕ </ci>  </apply>  </apply>  </annotation-xml>  </semantics>  </math> 
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 | | Cell[BoxData[RowBox[List[RowBox[List["HoldPattern", "[", FractionBox[RowBox[List[UnderoverscriptBox["\[Sum]", RowBox[List["k", "=", "0"]], RowBox[List["p_", "-", "1"]]], RowBox[List[SuperscriptBox[RowBox[List["JacobiDN", "[", RowBox[List[RowBox[List["z_", "+", FractionBox[RowBox[List["2", " ", "k", " ", RowBox[List["EllipticK", "[", "m_", "]"]]]], "p_"]]], ",", "m_"]], "]"]], "2"], " ", RowBox[List["(", RowBox[List[RowBox[List["JacobiDN", "[", RowBox[List[RowBox[List["z_", "+", FractionBox[RowBox[List["2", " ", RowBox[List["(", RowBox[List["k", "-", "1"]], ")"]], " ", RowBox[List["EllipticK", "[", "m_", "]"]]]], "p_"]]], ",", "m_"]], "]"]], "+", RowBox[List["JacobiDN", "[", RowBox[List[RowBox[List["z_", "+", FractionBox[RowBox[List["2", " ", RowBox[List["(", RowBox[List["k", "+", "1"]], ")"]], " ", RowBox[List["EllipticK", "[", "m_", "]"]]]], "p_"]]], ",", "m_"]], "]"]]]], ")"]]]]]], RowBox[List[UnderoverscriptBox["\[Sum]", RowBox[List["k", "=", "0"]], RowBox[List["p_", "-", "1"]]], RowBox[List["JacobiDN", "[", RowBox[List[RowBox[List["z_", "+", FractionBox[RowBox[List["2", " ", "k", " ", RowBox[List["EllipticK", "[", "m_", "]"]]]], "p_"]]], ",", "m_"]], "]"]]]]], "]"]], "\[RuleDelayed]", RowBox[List[FractionBox[RowBox[List[UnderoverscriptBox["\[Sum]", RowBox[List["k", "=", "0"]], RowBox[List["p", "-", "1"]]], RowBox[List[SuperscriptBox[RowBox[List["JacobiDN", "[", RowBox[List[FractionBox[RowBox[List["2", " ", "k", " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"], ",", "m"]], "]"]], "2"], " ", RowBox[List["(", RowBox[List[RowBox[List["JacobiDN", "[", RowBox[List[FractionBox[RowBox[List["2", " ", RowBox[List["(", RowBox[List["k", "-", "1"]], ")"]], " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"], ",", "m"]], "]"]], "+", RowBox[List["JacobiDN", "[", RowBox[List[FractionBox[RowBox[List["2", " ", RowBox[List["(", RowBox[List["k", "+", "1"]], ")"]], " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"], ",", "m"]], "]"]]]], ")"]]]]]], RowBox[List[UnderoverscriptBox["\[Sum]", RowBox[List["k", "=", "0"]], RowBox[List["p", "-", "1"]]], RowBox[List["JacobiDN", "[", RowBox[List[FractionBox[RowBox[List["2", " ", "k", " ", RowBox[List["EllipticK", "[", "m", "]"]]]], "p"], ",", "m"]], "]"]]]]], "/;", RowBox[List[RowBox[List["p", "\[Element]", "Integers"]], "&&", RowBox[List["p", "\[GreaterEqual]", "2"]]]]]]]]]] | 
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 | |  A. Khare, U. Sukhatme, "Cyclic Identities Involving Jacobi Elliptic Functions", math-ph/0201004, (2002) http://arXiv.org/abs/math-ph/0201004  A. Khare, U. Sukhatme, "Cyclic Identities Involving Jacobi Elliptic Functions", Journal of Mathematical Physics, v. 43, issue 7, pp. 3798-3806 (2002) | 
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