# NAG AD LibraryS (Specfun)Approximations of Special Functions

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S (Specfun) Chapter Introduction (FL Interface) – A description of the Chapter and an overview of the algorithms available.

Routine
Mark of
Introduction

Purpose
$\mathrm{ln}\left(1+x\right)$
Cumulative Normal distribution function $P\left(x\right)$
Complement of error function $\mathrm{erfc}\left(x\right)$
Modified Bessel functions ${I}_{\nu +a}\left(z\right)$, real $a\ge 0$, complex $z$, $\nu =0,1,2,\dots$