                    <img src="../images/chp04/not-smooth.svg" alt="Non smooth" title="Non smooth" style="width:100%;">
                            <figcaption>
                                Curve $C$ is not smooth since it has a cusp.
                            </figcaption>
                        </figure>
                    </div>
                </div>

                <p>
                    A <em>piecewise smooth curve</em> $C$
                    has a continuously turning tangent, except possibl