For 'Non intrinsic mathematical function" which library I have to insert/use ?

I'm not aware of such a library (couldn't find anything in help for vb6, if you're talking about .net then I have no idea). You may have to write your own functions (which is what the help file suggests). Someone out there has probably written a dll for it, but I don't know about it (which isn't actually saying much ;)). Formulas are here:

Secant: Sec(X) = 1 / Cos(X)
Cosecant: Cosec(X) = 1 / Sin(X)
Cotangent: Cotan(X) = 1 / Tan(X)
Inverse Sine: Arcsin(X) = Atn(X / Sqr(-X * X + 1))
Inverse Cosine: Arccos(X) = Atn(-X / Sqr(-X * X + 1)) + 2 * Atn(1)
Inverse Secant: Arcsec(X) = Atn(X / Sqr(X * X - 1)) + Sgn((X) - 1) * (2 * Atn(1))
Inverse Cosecant: Arccosec(X) = Atn(X / Sqr(X * X - 1)) + (Sgn(X) - 1) * (2 * Atn(1))
Inverse Cotangent: Arccotan(X) = Atn(X) + 2 * Atn(1)
Hyperbolic Sine: HSin(X) = (Exp(X) - Exp(-X)) / 2
Hyperbolic Cosine: HCos(X) = (Exp(X) + Exp(-X)) / 2
Hyperbolic Tangent: HTan(X) = (Exp(X) - Exp(-X)) / (Exp(X) + Exp(-X))
Hyperbolic Secant: HSec(X) = 2 / (Exp(X) + Exp(-X))
Hyperbolic Cosecant: HCosec(X) = 2 / (Exp(X) - Exp(-X))
Hyperbolic Cotangent: HCotan(X) = (Exp(X) + Exp(-X)) / (Exp(X) - Exp(-X))
Inverse Hyperbolic Sine: HArcsin(X) = Log(X + Sqr(X * X + 1))
Inverse Hyperbolic Cosine: HArccos(X) = Log(X + Sqr(X * X - 1))
Inverse Hyperbolic Tangent: HArctan(X) = Log((1 + X) / (1 - X)) / 2
Inverse Hyperbolic Secant: HArcsec(X) = Log((Sqr(-X * X + 1) + 1) / X)
Inverse Hyperbolic Cosecant: HArccosec(X) = Log((Sgn(X) * Sqr(X * X + 1) + 1) / X)
Inverse Hyperbolic Cotangent: HArccotan(X) = Log((X + 1) / (X - 1)) / 2
Logarithm to base N: LogN(X) = Log(X) / Log(N)