Wolfram Language & System 11.0 (2016)|Legacy Documentation

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gives the modified Bessel function of the second kind .


  • Mathematical function, suitable for both symbolic and numerical manipulation.
  • satisfies the differential equation .
  • BesselK[n,z] has a branch cut discontinuity in the complex z plane running from to .
  • FullSimplify and FunctionExpand include transformation rules for BesselK.
  • For certain special arguments, BesselK automatically evaluates to exact values.
  • BesselK can be evaluated to arbitrary numerical precision.
  • BesselK automatically threads over lists.
Introduced in 1988
| Updated in 1999