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they do not incline or bow so much to one another, as the Sides of the Angle CAB. Tο understand which, you need only conceive the Angle DAF to be laid upon the Angle CAB, as you may see by the dotted Lines representing the Angle DAF.

Here Note, That when I express an Angle by three Letters, that Letter in the middle exprefses the Point wherein the Sides meet, which is called the angular Point. As the Angle DAF shews the Angle formed by the two Lines or Sides DA, AF; it being the angular Point wherein the Sides meet.

Moreover, right-lined Angles are such, whose Sides are right Lines; and curved-lined ones such, whose Sides are crooked Lines.

9. When the Lines that contain or form an Angle are right ones, that Angle is called a Right-lined Angle.

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10. When a right Line CG, standing upon a right Line AB, makes the Angles CGA, CGB, on each fide equal to one another, each of those equal Angles is call'd a Right Angle;

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B and the right Line CG

thus standing, is called

a Perpendicular to the Line AB, upon which it stands.

11. An

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C

B

⚫gle; as ACB.

12. An Acute An

Dgle is that which is less than a right Angle ; as ACD.

13. A Term or Bound is the Extremity or End of any thing.

14. A Figure is that which is contained under one or more Terms or Bounds.

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15. A Circle is a plane Figure contained under one Line, which is called the Circumference; to which all Lines that fall from a certain Point within the Figure, are equal to one another.

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16. And that Point is called the Center of the Circle.

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18. A Semi-circle is a Figure which is contained under the Diameter, and under that part of the Circumference which is cut off by the Diameter.

In the Circle EABCD, the Point E is the Center, the Line AC the Diameter, and ABC is a Semi-circle.

19. Right-lined Figures are such as are contained under right Lines.

20. Trilateral or three-fided Figures are such as

are contained under three right Lines.

21. Quadrilateral or four-fided Figures are such

as are contained under four right Lines.

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22. Mul

22. Multilateral or many-fided Figures, are such as are contained under more right Lines than four.

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ne one Figure be equal to the several the other. The same is to be under

equilateral Figures.

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32. A Rhom-.. boides, is a Figure whose opposite Sides and

opposite Angles

are only equal;

Sides being not equal between themnor the Angles right ones; as CLMH.

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A

B

34. Parallel, or Equidistant right Lines, are fuch, which being in the same plain Su

perficies, if infinitely produced, would never meet;

as A and B.

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meter in one or the same Point G, are drawn so, that the Parallelogram be divided by them into four Parallelograms; then those two Parallelograms, DG and GB, thro' which the Diameter does not pass, are called Complements; and the other two, HE, FI, which the Diameter passeth thro', are called Parallelograms standing about the Diameter.

A Definition is what determines the Idea of a Word, or which gives a clear Notion of the Thing that we would have fignified by that Word.

An Axiom is that which is so evident, that it has no need of a Proof; as that the Whole is greater than its Part, &c.

A Theorem is something proposed, the Truth of which is to be made appear (which is called demonftrating it) so evidently, that all scruple

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