function value = circle_sector_area_2d ( r, center, theta1, theta2 )

%% CIRCLE_SECTOR_AREA_2D returns the area of a circular sector in 2D.
%
%  Discussion:
%
%    A sector is contained within a circular arc and the lines joining each
%    endpoint of the arc to the center of the circle.
%
%  Modified:
%
%    05 May 2005
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, double precision R, the radius of the circle.
%
%    Input, double precision CENTER(2), the center of the circle.
%
%    Input, double precision THETA1, THETA2, the angles of the rays
%    that delimit the sector.
%
%    Output, double precision CIRCLE_SECTOR_AREA_2D, the area of the sector.
%
  value = 0.5 * r * r * ( theta2 - theta1 );