There are three types of conics&colon; the ellipse, parabola, and hyperbola. Thus there is a 2-way classification&colon; ellipse/hyperbola and parabola. The mirrors are usually a section of a rotated parabola and a hyperbola, or ellipse. These correspond respectively to the limiting forms of an ellipse, parabola, and a hyperbola. A rectangular hyperbola has asymptotes that are perpendicular to each other. For we obtain an ellipse, for a parabola, and for a hyperbola. Define by the equations for an ellipse and for a hyperbola. The midpoint of a segment connecting a hyperbola's vertices is the center of the hyperbola. The diagonals are the semi-axes formula 147 of the hyperbola. The shape of the invariant hyperbola corresponds to a path of constant proper acceleration. The foci of the hyperbola formula 72 are formula 73. The eccentricity of a rectangular hyperbola is formula 17. The tangents may belong to points on different branches of the hyperbola. Thus it is the distance from the center to either vertex of the hyperbola. That means, in general formula 300 are "not" the vertices of the hyperbola.