///withoutPrompt 
function y=F(x)
  if x<0 then
    y=-a*cos(f*x)
  else
    y=a*(-2+cos(b*f*x))
  end
endfunction

function y=Fx(x)
  if x<0 then
    y=a*f*sin(f*x)
  else
    y=-a*f*b*sin(b*f*x)
  end
endfunction ///\withPrompt{}