[b]LARGE POINTS[/b] are moveable. The points along the curve stay on the dashed grid. To move the dashed line, move any of the 2 points that lie on it. [br][br]Click on any point lying on the dashed line and then drag it to move it within the plane containing the grid.  [br][img width=230,height=230]https://lh4.googleusercontent.com/mBhWuagIZuoXEmUiq0MuGrE44wcQ5_yy9g1uOFC-dcF5wt14SFJ1dsSOYdMf4XkiCLkxh7QSFIGhiXmWyQQokCx6VYe1taI-aSt2WneziDEk9h9e6TL8l3nmQYg9Im3fso1A3k-9[/img][br][br]Click on this point again and then drag it up or down to move it off the plane containing the grid. [br][img width=230,height=230]https://lh4.googleusercontent.com/2YnE4ZcJ_qpLSBrATUWCW2jY7GhMaS_jtENddBqo1lBROjX154xtmE2NC7gkQO5UW18Te4FqGDFbG-ZFxOazR5G8IHStuz5hGdtfHjaTje-XnTY1zwGYtyax0JYR_ArVq6ltWYzz[/img][br][br]Move the point with the arrows to spin the curve about the dashed line to form the surface of revolution. [br][img width=184,height=186]https://lh5.googleusercontent.com/oqJJRZc9dNKwgdRvKMCtqpY9gfj2Frdl6rpcqwt4_mT4QpU2tiSWz1BuFreYiBXns91bkjWRGqYCvq9HVGzpTpoUHvM_0K_FZzrhZA3dQo3qS3uYD06Xqb4s9KoWMwWV9JveFn8w[/img]