10 Bessel FunctionsModified Bessel Functions

§10.29 Recurrence Relations and Derivatives

Contents
  1. §10.29(i) Recurrence Relations
  2. §10.29(ii) Derivatives

§10.29(i) Recurrence Relations

With 𝒵ν⁡(z) defined as in §10.25(ii),

10.29.1 𝒵ν−1⁡(z)−𝒵ν+1⁡(z) =(2⁢ν/z)⁢𝒵ν⁡(z),
𝒵ν−1⁡(z)+𝒵ν+1⁡(z) =2⁢𝒵ν′⁡(z).
10.29.2 𝒵ν′⁡(z) =𝒵ν−1⁡(z)−(ν/z)⁢𝒵ν⁡(z),
𝒵ν′⁡(z) =𝒵ν+1⁡(z)+(ν/z)⁢𝒵ν⁡(z).
10.29.3 I0′⁡(z) =I1⁡(z),
K0′⁡(z) =−K1⁡(z).

For results on modified quotients of the form z⁢𝒵ν±1⁡(z)/𝒵ν⁡(z) see Onoe (1955) and Onoe (1956).

§10.29(ii) Derivatives

For k=0,1,2,…,

10.29.4 (1z⁢ddz)k⁡(zν⁢𝒵ν⁡(z)) =zν−k⁢𝒵ν−k⁡(z),
(1z⁢ddz)k⁡(z−ν⁢𝒵ν⁡(z)) =z−ν−k⁢𝒵ν+k⁡(z).
10.29.5 𝒵ν(k)⁡(z)=12k⁢(𝒵ν−k⁡(z)+(k1)⁢𝒵ν−k+2⁡(z)+(k2)⁢𝒵ν−k+4⁡(z)+⋯+𝒵ν+k⁡(z)).