The curvature κ\kappaκ of a plane curve r(t)=⟨x(t),y(t)⟩\mathbf{r}(t) = \langle x(t), y(t) \rangler(t)=⟨x(t),y(t)⟩ is defined by which formula?
∣r′(t)⋅r′′(t)∣∣r′(t)∣3\frac{|\mathbf{r}'(t) \cdot \mathbf{r}''(t)|}{|\mathbf{r}'(t)|^3}∣r′(t)∣3∣r′(t)⋅r′′(t)∣
∣x′y′′−y′x′′∣(x′2+y′2)3/2\frac{|x'y'' - y'x''|}{(x'^2 + y'^2)^{3/2}}(x′2+y′2)3/2∣x′y′′−y′x′′∣
∣x′y′−x′′y′′∣(x′2+y′2)\frac{|x'y' - x''y''|}{(x'^2 + y'^2)}(x′2+y′2)∣x′y′−x′′y′′∣
∣r′′(t)∣/∣r′(t)∣|\mathbf{r}''(t)| / |\mathbf{r}'(t)|∣r′′(t)∣/∣r′(t)∣