is a hyperbola, and a is the semi transverse axis. (As described in Chapter 2, c is the semi transverse axis of the conjugate hyperbola.) If this figure is rotated about the z-axis through...is a hyperbola, and a is the semi transverse axis. (As described in Chapter 2, c is the semi transverse axis of the conjugate hyperbola.) If this figure is rotated about the z-axis through 360∘, the surface swept out is a circular hyperboloid (or hyperboloid of revolution) of one sheet. If the figure is rotated about the x-axis through 360∘, the surface swept out is a circular hyperboloid (or hyperboloid of revolution) of two sheets.