« PreviousContinue »
I. Point is that which hath no parts, or which hath no mag. See Noten nitude.
II. A line is length without breadth.
II. The extremities of a line are points. .
VII. A plane superficies is that in which any two points being taken, See Na the straight line between them lies wholly in that superficies.
VIII. • A plane angle is the inclination of two lines to one another Scc N:
“ in a plane, which meet together, but are not in the same
lines to one another, which meet together, but are not in
• N. B.
•N. B. When several angles are at one point B, any one of them is expressed by three letters, of which the letter that ' is at the vertex of the angle, that is, at the point in which • the straight lines that contain the angle meet one another, is
put between the other two letters, and one of these two is • fomewhere upon one of those straight lines, and the other
upon the other line: Thus the angle which is contained by the straight lines AB, CB is named the angle ABC, or CBA; . that which is contained by AB, DB is named the angle • ABD, or DBA; and that which is contained by DB, CB is
called the angle DBC, or CBD; but, if there be only one angle “at a point, it may be expressed by a letter placed at that point; • as the angle at E.'
ther straight line makes the adjacent
led the circumference, and is such that all straight lines
XVII. A diameter of a circle is a straight line drawn through the Se NI centre, and terminated both ways by the circumference.
XVIII. A semicircle is the figure contained by a diameter and the part of the circumference cut off by the diameter.
XIX. « A segment of a circle is the figure contained by a straight « line and the circumference it cuts off.”
XXIII. Multilateral figures, or polygons, by more than four straight lines.
equal, and all its angles right angles.
are not right angles.
XXXII. See N. A rhomboid, is that which has its opposite fides equal to one
another, but all its Gdes are not equal, nor its angles right angles.