zài / zhè / tiáo / qū / xiàn / shàng / qū / lǜ / xiàng / liàng / shǐ / zhōng / zhǐ / xiàng / qū / xiàn / āo / de / yí / cè

在这条曲线上，曲率向量始终指向曲线凹的一侧。

Along this curve, the curvature vector always points toward the concave side of the curve.