OPHIUCUS

, a constellation of the northern hemisphere; called also Serpentarius.

OPPOSITE Angles, or Vertical Angles, are those opposite to each other, made by two intersecting lines; as a and b, or c and d.—The opposite angles are equal to each other.

Opposite Cones, denote two similar cones vertically opposite, having the same common vertex and axis, and the same sides produced; as the cones A and B.

Opposite Sections, or Hyperbolas, are those made by cutting the Opposite cones by the same plane; as the hyperbolas C and D.—These are always equal and similar, and have the same transverse axis EF, as also the same conjugate axis.