Which expression describes the differential arc length dsdsds for a path r(t)=⟨x(t),y(t)⟩\mathbf{r}(t) = \langle x(t), y(t) \rangler(t)=⟨x(t),y(t)⟩?
dx+dydx + dydx+dy
(dxdt)2+(dydt)2dt\sqrt{(\frac{dx}{dt})^2 + (\frac{dy}{dt})^2} dt(dtdx)2+(dtdy)2dt
dxdt⋅dydt\frac{dx}{dt} \cdot \frac{dy}{dt}dtdx⋅dtdy
x2+y2dt\sqrt{x^2 + y^2} dtx2+y2dt