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Page 18. line 24. from the foot, omitted (margin) a 5. 1. 3. from the top, for AC is read AG is
93. 136. 196. 196.
12. from the foot, for tirangle read triangle
13. from the foot, for HBC. And read HBC, and
2. from the top, for any angle read an angle
16.&43. from the top, for Proctus read Proclus
Befides thefe, in the 4th line of the Note to PROB. IX. in p. 320. there is ADE, instead of ADB, and Pl. I. Fig. 16. is omitted in the margin oppofite to PROB. X.; and in p. 325. in the first line of the last column of the Table, there is 13, inftead of 18.
A ftraight line is that which lies evenly between its extreme points.
A fuperficies is that which hath only length and breadth.
The extremities of a fuperficies are lines.
A plane fuperficies is that in which any two points being taken, the straight line between them lies wholly in that fuperficies.
A plane rectilineal angle is the inclination of two ftraight lines to one another, which meet together, but are not in the fame straight line.
‹ N. B. When feveral angles are at one point B, any one of them is expreffed by three letters, of which the letter that is at the vertex of the angle, that is, at the point in which the ftraight 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 thofe ftraight lines, and the other upon the other line: Thus, the angle which is contained by the ftraight 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 expreffed by a letter placed at that point; as the angle at E.'
When a ftraight line ftanding on ano-
An obtufe angle is that which is greater than a right angle.
An acute angle is that which is less than a right angle.
A figure is that which is inclosed by one or more boundaries.
Any ftraight line drawn from the center to the circumference of a circle, is called a Radius.
A diameter of a circle is a ftraight line drawn through the centre, and terminated both ways by the circumference.
A femicircle is the figure contained by a diameter and the part of the circumference cut off by the diameter.
Rectilineal figures are thofe which are contained by straight
Trilateral figures, or triangles, by three ftraight lines.
Quadrilateral, by four ftraight lines,
Multilateral figures, or polygons, by more than four straight lines.
Of three-fided figures, an equilateral triangle is that which has three equal fides.
An Ifofceles triangle, is that which has only two fides equal.
A scalene triangle, is that which has three unequal fides.
A right angled triangle, is that which has a right angle.
An obtufe angled triangle, is that which has an obtufe angle.
An acute angled triangle, is that which has three acute angles.
Of four-fided figures, a fquare is that which has all its fides equal, and all its angles right angles.
An oblong, is that which has all its angles right angles, but has not all its fides equal.
A rhombus, is that which has all its fides equal, but its angles are not right angles.
A rhomboid, is that which has its oppofite fides equal to one another, but all its fides are not equal, nor its angles right angles.
All other four-fided figures, befides these, are called Trapeziums.
Parallel ftraight lines, are fuch as are in