NAME
    cosh - hyperbolic cosine

SYNOPSIS
    cosh(x [,acc])

TYPES
    x		real
    acc		real

    return	real

DESCRIPTION
    Calculate the hyperbolic cosine of x with an accuracy within acc.
    By default, acc is epsilon().

    The hyperbolic cosine is calculated using the formula:

	cosh(x) = (exp(x) + exp(-x)) / 2

EXAMPLE
    > print cosh(-1), cosh(0), cosh(2^-17)
    ~1.54308063481524377847 1 ~1.00000000002910383045

    > print cosh(0.4), cosh(0.4, 0.01), cosh(acosh(1), 0.001)
    ~1.08107237183845480928 1.0810546875 1

LIMITS
    x < 2^100000
    acc > 0

LIBRARY
    NUMBER *qcosh(NUMBER *x, *acc)

SEE ALSO
    acosh, asinh, atanh, epsilon, sinh, tanh
