path: root/misc/pascal/tests/src/101-cosine.pas

{ compute the cosine using the expansion:
  cos(x) = 1 - x**2/(2*1) + x**4/(4*3*2*1) - ... }

program cosine(input, output);

const
   eps = 1e-14;

var
   x, sx, s, t : real;
   i, k, n     : integer;

begin
   write('Number of cosines: ');
   read(n);
   for i:=1 to n do
   begin
      write(n, '. Enter radians: ');
      read(x);
      t := 1; k := 0; s := 1; sx := sqr(x);
      while abs(t) > eps*abs(s) do
      begin
	 k := k+2;
	 t := -t*sx/(k*(k-1));
	 s := s+t;
	 writeln('   cos(', x, ')=', s, ' interation=', k div 2)
      end
   end
end.