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Conic Sections Lesson #1: Introducing Conic Sections The Double-Napped Cone Class Ex. #1 Li A cone is a solid which can be generated by rotating a right angled triangle about one of its legs. ~~ A double-napped cone is formed when the vertices of two cones are placed together. For example, we can make a double-napped cone by: * taking two water cups shaped as cones and placing their tips against each other, or, ¢ placing a lecture pointer stick between your thumb and finger, holding it vertically in front of you, and then rotating it so that the top of the pointer and the bottom of the pointer form circles. In general, a double-napped cone is produced by rotating an oblique line (called the generator) about an axis. If the line is parallel to the generator, a cylinder is formed. This case will be discussed later. A double-napped cone consists of the following parts: generator, upper nappe, lower nappe, vertex, axis of symmetry (called the central axis), generator angle, and vertex angle. axis of SH A Syrome ey a) the generator %) Label the following on the diagram. b) upper nappe veree Nappe c) lower nappe d) vertex Genecatot angle Arecten e) axis of symmetry veeter angle f) generator angle Jower NOappe g) vertex angle PP 
