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- #1

The Frenet Equations are

\begin{align*}

\frac{d\hat{\mathbf{u}}}{ds} &= \frac{1}{\rho}\hat{\mathbf{n}}\\

\frac{d\hat{\mathbf{b}}}{ds} &= -\frac{1}{\tau}\hat{\mathbf{n}}\\

\frac{d\hat{\mathbf{n}}}{ds} &= \frac{1}{\tau}\hat{\mathbf{b}} - \frac{1}{\rho}\hat{\mathbf{u}}

\end{align*}

The torsion in terms of time derivatives is

\begin{align*}

\tau &= \frac{\dot{\mathbf{r}}\times \ddot{\mathbf{r}}\cdot\ddot{\mathbf{r}}}

{\lvert\dot{\mathbf{r}}\times \ddot{\mathbf{r}}\rvert^2}

\end{align*}

I am not sure how to go from the equations to answer though.