Calculates the hyperbolic arc cosine of a floating-point number.

[Format]

#include <math.h>

double acosh(double d);

float acoshf(float d);

long double acoshl(long double d);

[Parameters]

d Floating-point number for which hyperbolic arc cosine is to be computed

[Return values]

Normal: Hyperbolic arc cosine of d

Abnormal: Domain error: Returns NaN.

Error conditions: A domain error occurs when d is smaller than 1.0.

[Remarks]

The acosh function returns the hyperbolic arc cosine in the range [0, +∞].