Wolfram Language & System 10.4 (2016)|Legacy Documentation

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gives the modified Bessel function of the first kind .


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