NAME
    asech - inverse hyperbolic secant

SYNOPSIS
    asech(x [,eps])

TYPES
    x		real, 0 < x <= 1
    eps		nonzero real, defaults to epsilon()

    return	real

DESCRIPTION
    Returns the asech of x to a multiple of eps with error less in
    absolute value than .75 * eps.

    asech(x) is the real number v for which sech(v) = x.  It is given by

    		asech(x) = ln((1 + sqrt(1 - x^2))/x)

EXAMPLE
    > print asech(.5,1e-5), asech(.5,1e-10), asech(.5,1e-15), asech(.5,1e-20)
    1.31696 1.3169578969 1.316957896924817 1.31695789692481670862

LIMITS
    none

LIBRARY
    NUMBER *qasech(NUMBER *x, NUMBER *eps)

SEE ALSO
    asinh, acosh, atanh, acsch, acoth, epsilon