短語詞組短語Brachistochrone Curve 最速曲線;最速降線問題brachistochrone problem 最速降線問題;線問題problem of brachistochrone 最速降線的問題;最速降線問題The brachistochrone problem 最速落逕問題brachistochrone with bounded curvature 界曲率最速降線 返回 brachistochrone