MENSURATION. DEFINITIONS. I. A POINT is that which has no parts, or which has no magnitude. 2. A line is length without breadth. 3. The extremities of a line are points. 4. A straight line is that which lies evenly between its extreme points. 5. A superficies is that which has length and breadth. 6. A plane superficies is that in which any two points being taken, the straight line between them lies wholly in that superficies. 7. 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. T. M. I 12. And this point is called the centre of the circle (C). 13. A radius is a straight line drawn from the centre to the circumference (CD). 14. A diameter is a straight line drawn through the centre, and terminated both ways by the circumference (AB). 15. A semicircle is the figure contained by a diameter and part of the circumference cut off by the diameter (ADB). |