%OPP Returns the equal but opposite vector
% OPP(VECTOR) returns the vector acting in the opposite direction to the
% input vector.
% See also MAG, MOVE.
% Details are to be found in Mastering Mechanics I, Douglas W. Hull,
% Prentice Hall, 1998
% Douglas W. Hull, 1998
% Copyright (c) 1998-99 by Prentice Hall
% Version 1.00
[xmag ymag xcor ycor]=breakup(inVector);
outVector=[-xmag -ymag xcor ycor];