function ds2(omega, r, t, d) 
  -(omega^2*r^4*sin(omega*t)^4+sqrt(d^2-r^2*sin(omega*t)^2)*(omega^2*r^3*cos(omega*t)*sin(omega*t)^2-d^2*omega^2*r*cos(omega*t))-2*d^2*omega^2*r^2*sin(omega*t)^2+d^2*omega^2*r^2)/(sqrt(d^2-r^2*sin(omega*t)^2)*(r^2*sin(omega*t)^2-d^2))
endfunction
