Chi Ci Shi Si

Chi() Function Chi ( X As  Double, Optional Info As  Long  ) Hyperbolic cosine integral Chi(x) Purpose This routine computes the hyperbolic cosine integral. Chi(x) = ∫ (cosh(t)-1)/t dt [0, x] + ln(x) + γ (γ: Euler's constant) Returns Double Hyperbolic cosine integral Chi(x). Parameters [in] X Argument x. (x != 0) (If x < 0, returns the real part = Chi(|x|)) [out] Info (Optional) = 0: Successful exit. = -1: The argument X had an illegal value. (X = 0) = 1: Floating point range error.