Digital Library of Mathematical Functions
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22 Jacobian Elliptic FunctionsProperties

§22.6 Elementary Identities

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§22.6(ii) Double Argument

See also Carlson (2004).

§22.6(iii) Half Argument

If \{\mbox{p,q,r}\} is any permutation of \{\mbox{c,d,n}\}, then

22.6.22{\mathop{\mathrm{pq}\/}\nolimits^{{2}}}\left(\tfrac{1}{2}z,k\right)=\frac{%
\mathop{\mathrm{ps}\/}\nolimits\left(z,k\right)+\mathop{\mathrm{rs}\/}%
\nolimits\left(z,k\right)}{\mathop{\mathrm{qs}\/}\nolimits\left(z,k\right)+%
\mathop{\mathrm{rs}\/}\nolimits\left(z,k\right)}=\frac{\mathop{\mathrm{pq}\/}%
\nolimits\left(z,k\right)+\mathop{\mathrm{rq}\/}\nolimits\left(z,k\right)}{1+%
\mathop{\mathrm{rq}\/}\nolimits\left(z,k\right)}=\frac{\mathop{\mathrm{pr}\/}%
\nolimits\left(z,k\right)+1}{\mathop{\mathrm{qr}\/}\nolimits\left(z,k\right)+1}.

For (22.6.22) and similar results, see Carlson (2004).

§22.6(iv) Rotation of Argument (Jacobi’s Imaginary Transformation)

§22.6(v) Change of Modulus

See §22.17.