function dydt = ripple_deriv ( t, y )

%*****************************************************************************80
%
%% ripple_deriv() evaluates the derivative of the ripple ODE.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    06 November 2020
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    John D Cook,
%    Ripples and Hyperbolas,
%    https://www.johndcook.com/blog/2020/11/06/ripples-and-hyperbolas/
%    Posted 06 November 2020.
%
%    Wendell Mills, Boris Weisfeiler, Allan Krall,
%    Discovering Theorems with a Computer: The Case of y‘ = sin(xy). 
%    The American Mathematical Monthly, 
%    Volume 86, Number 9, November 1979, pages 733-739.
%
%  Input:
%
%    real T, Y: the arguments of the derivative.
%
%  Output:
%
%    real DYDT: the value of the derivative.
%
  dydt = sin ( t * y );

  return
end
