chi ci shi si

chi() double chi ( double  x ) Hyperbolic cosine integral Chi(x) Purpose chi computes the hyperbolic cosine integral. Chi(x) = ∫ (cosh(t)-1)/t dt [0, x] + ln(x) + gamma (gamma: Euler's constant) Returns Hyperbolic cosine integral Chi(x). Parameters [in] x Argument x. (x != 0) (If x < 0, returns the real part = Chi(|x|)) Error handling If x = 0, -inf is returned and range error (ERANGE) occurs. Other range error (ERANGE) may occur.