% COSD COSD Cosine Degrees Function
% 
% Usage
% 
% Computes the cosine of the argument, but takes
% the argument in degrees instead of radians (as is the case
% for cos). The syntax for its use is
% 
%    y = cosd(x)
% 
function y = cosd(x)
  if (nargin == 0 || ~isnumeric(x) || ~isreal(x))
    error('cosd expects a numeric input');
  end
  y = cos(deg2rad(x));