# proof - curvature of plane curve

Well, what do you know about "curvature" and what formulas do you have for it? I suspect there are a number of different proofs of this starting from different formulas. You might, for example, use the fact that the curvature is $\left|\frac{dT}{ds}\right|$ where T is the unit tangent vector and s is the arclength. You would need to relate both parameters to the arclength. Then basically use the chain rule.