To find the Superficies of the Frustum of a Cone, To find the Solidity of the Fruftum of a Cone or Pyramid, 181 GEOMETRICAL DEFINITIONS. i. A POINT is that which has no parts, neither length, breadth, nor thickness. 2. A line is length, without breadth or thickness. 3. A furface, or superficies, is that which has length and breadth, without thickness. 4. A folid is that which has length, breadth, and thickness. 5. Points are the extremities of a line. 6. Lines are the boundaries of a fuperficies. 7. Superficies are the boundaries of a folid. 8. A ftraight line lies evenly between its extreme points. See plate 1. fig. 1. 9. Parallel lines are such as are in the fame plane, and keep the fame distance, though produced ever fo far. 10. An angle is the inclination of two lines of different directions, and meeting in a point. See plate 1. fig. 2. N. B. When two lines, AB, and BC, meet in any point, 11. When one straight line falls upon another straight line, so as to make the adjacent angles equal to one another, each of them is a right angle and the straight line which falls upon the other is perpendicular to it. See plate 1. fig. 3. 12. An angle which is less than a right angle, is called an acute angle. See plate 1. fig. 4. |