Chapter 12.5, Problem 3QCE

Suppose that C is the graph of a smooth vector-valued function $\text{r}\left(s\right)=〈x\left(s\right),y\left(s\right)〉$ parametrized by arc length and that the unit tangent $\text{T}\left(s\right)=〈\text{cos}\varphi \left(s\right),\text{sin }\varphi \left(s\right)〉.$ Then the curvature can be expressed in terms of $\varphi \left(s\right)\text{as}\kappa \left(s\right)= \text{\_\_\_\_\_\_\_\_}\text{.}$