NAME
    vercos - versed trigonometric cosine

SYNOPSIS
    vercos(x [,eps])

TYPES
    x		number (real or complex)
    eps		0 < real < 1, defaults to epsilon()

    return	number

DESCRIPTION
    Calculate the versed trigonometric cosine of x to a multiple of eps with error less in
    absolute value than .75 * eps.

    This function is sometimes called verc, is equivalent to:

	vercos(x) = 1 + cos(x)

EXAMPLE
    ; print vercos(0.2), vercos(3/7), vercos(-31)
    1.98006657784124163112 1.90956035167416667403 1.91474235780453127896

    ; print vercos(1, 1e-5), vercos(1, 1e-10), vercos(1, 1e-15), vercos(1, 1e-20)
    1.5403 1.5403023059 1.54030230586814 1.5403023058681397174

    ; print vercos(2 + 3i, 1e-5), vercos(2 + 3i, 1e-10)
    -3.18963-9.10923i -3.189625691-9.1092278938i

    ; pi = pi(1e-20)
    ; print vercos(pi/3, 1e-10), vercos(pi/2, 1e-10), vercos(pi, 1e-10), vercos(3*pi/2, 1e-10)
    1.5 1 0 1

LIMITS
    0 < eps < 1

LINK LIBRARY
    NUMBER *qvercos(NUMBER *x, NUMBER *eps)
    COMPLEX *c_vercos(COMPLEX *x, NUMBER *eps)

SEE ALSO
    sin, cos, tan, cot, sec, csc
    asin, acos, atan, acot, asec, acsc
    versin, coversin, vercos, avercos
    aversin, acoversin, covercos, acovercos
    epsilon

## Copyright (C) 2023  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
## or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL.  You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
##
## Under source code control:	2023/09/05 23:25:28
## File existed as early as:	2023
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/