Calculus: Early Transcendentals 8th Edition

We know that at an inflection point (where $f$ is twice continuously differentiable), we must have $f''(x)=0$. The curvature is given by: $\kappa(x)=\frac{|f''(x)|}{[1+(f'(x))^2]^{3/2}}$ Plugging in $f''(x)=0$, we get $\kappa(x)=0$. Thus the curvature must be zero. True.