

   TTrriiggoonnoommeettrriicc FFuunnccttiioonnss

        cos(x)
        sin(x)
        tan(x)
        acos(x)
        asin(x)
        atan(x)
        atan2(y, x)

   DDeessccrriippttiioonn::

        These functions give the obvious trigonometric func-
        tions.  They respectively compute the cosine, sine,
        tangent, arc-cosine, arc-sine, arc-tangent and arc-tan-
        gent of two arguments.

   SSeeee AAllssoo::

        `Log', `Math'.

   EExxaammpplleess::

        x <- 1:99/100
        all(Mod(1 - (cos(x) + 1i*sin(x)) / exp(1i*x)) < 1.1 * .Machine$double.eps)
         2* abs(1 - x / acos(cos(x))) / .Machine$double.eps #-- depends ?
        all(abs(1 - x / asin(sin(x))) <= .Machine$double.eps) # TRUE (Solaris)
        all(abs(1 - x / atan(tan(x))) <= .Machine$double.eps) # TRUE (Solaris)

