BOOK IV.
DEFINITIONS.
1. A rectilneal figure is said to be inscribed in another rectilineal figure, when all the angles of the inscribed figure are on the sides of the figure in which it is inscribed, each on each.
2. In like manner, a figure is said to be described about another figure, when all the sides of the circumscribed figure pass through the angular points of the figure about which it is described, each through each.
3. A rectilineal figure is said to be inscribed in a circle, when all the angles of the inscribed figure are on the circumference of the circle.
4. A rectilineal figure is said to be described about a circle, When each side of the circumscribed figure touches the circumference of the circle.
5. In like manner, a circle is said to be inscribed in a rectilineal figure, when the circumference of the circle ouches each side of the figure.
