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acosh, acoshf
[inverse hyperbolic cosine]

SYNOPSIS

    #include <math.h>
    double acosh(double x);
    float acoshf(float x);

DESCRIPTION

acosh calculates the inverse hyperbolic cosine of x.
acosh is defined as:

x must be a number greater than or equal to 1.

acoshf is identical, other than taking and returning floats.

RETURN

acosh and acoshf return the calculated value. If x less than 1, the return value is NaN and errno is set to EDOM.

You can change the error-handling behavior with the non-ANSI matherr function.

COMPLIANCE

Neither acosh nor acoshf are ANSI C.

They are not recommended for portable programs.