“the PRINciples of the differential calculus,” “outlines of LONDON : EUCLID’S ELEMENTS OF GEOMETRY. BOOK I. DEFINITIONS. I. A PosNT is that which hath no parts, or which hath no magnitude. II. A line is length without breadth. III. The extremities of a line are points. IV. A straight line is that which lies evenly between its extreme points. V. A superficies is that which hath only length and breadth. VI. The extremities of a superficies are lines. VII. A plane superficies is that in which any two points being taken, the straight line between them lies wholly in that superficies. VIII. “A plane angle is the inclination of two lines to one another in a plane, which meet together, but are not in the same direction.” IX. A plane rectilineal angle is the inclination of two straight lines to one another, which meet together, but are not in the same straight line. e. B |