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QUANTIT 1. UANTITY, or Magnitude, is any thing that will admit of increase or decrease ; or that is capable of any sort of calculation or mensuration: such as numbers, lines, space, time, motion, weight.

2. MATHEMATICs is the science which treats of all kinds of quantity whatever, that can be numbered or measured.That part which treats of numbering is called Arithmetic ; and that which concerns measuring, or figured extension, is called Geometry. These two, which are conversant about multitude and magnitude, being the foundation other parts, are called Pure or Abstract Mathematics ; because they investigate and demonstrate the properties of abstract numbers and magnitudes of all sorts. And when these two parts are applied to particular or practical subjects, they constitute the branches or parts called Mixed Mathematics. Mathematics is also distinguished into Speculative and Practical : viz. Speculative, when it is concerned in discovering properties and relations; and Practical, when applied to practice and real use concerning physical objects. VOL. I.

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3. In Mathematics are several general terms or principles ; such as, Definitions, Axioms, Propositions, Theorems, Prob. lems, Lemmas, Corollaries, Scholiums, &c.

4. A Definition is the explication of any term or word in a science; showing the sense and meaning in which the term is employed.-Every Definition ought to be clear, and expressed in words that are common and perfectly well understood

5. A Proposition is something proposed to be proved, or something required to be done ; and is accordingly either a Theorem or a Problem.

6. A Theorem is a demonstrative proposition; in which some property is asserted, and the truth of it required to be proved. Thus, when it is said that, The sum of the three angles of any triangle is equal to two right angles, this is a Theorem, the truth of which is demonstrated by Geometry. -A set or collection of such Theorems constitutes a Theory.

7. A Problem is a proposition or a question requiring something to be done ; either to investigate some truth or property, or to perform some operation. As, to find out the quantity or sum of all the three angles of any triangle, or to draw one line perpendicular to another.--Å Limited Problem is that which has but one answer or solution. An Unlimited Problem is that which has innumerable answers. And a Determinate Problem is that which has a certain number answers.

8. Solution of a Problem, is the resolution or answer given to it. A Numerical or Numeral Solution, is the answer given in numbers. A Geometrical Solution, is the answer given by the principles of Geometry. And a Mechanical Solution, is one which is gained by trials.

9. A Lemma is a preparatory proposition, laid down in order to shorten the demonstration of the main proposition which follows it.

10. A Corollary, or Consectary, is a consequence drawn immediately from some proposition or other premises.

11 A Scholium is a remark or observation made on some foregoing proposition or premises.

12. An Acion, or Maxim, is a self-evident proposition ; requiring no formal demonstration to prove the truth of it; but is received and assented to as soon as mentioned. Such as, The whole of any thing is greater than a part of it; or, The whole is equal to all its parts taken together : or, Two quantities that are each of them equal to a third quantity, are equal to each other.

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13. A Postulate, or Petition, is something re uired to be done, which is so easy and evident that no person will hesitate to allow it.

14. An Hypothesis is a supposition assumed to be true, in order to argue from, or to found upon it the reasoning and demonstration of some proposition.

15. Demonstration is the collecting the several arguments and proofs, and laying them together in proper order, to show the truth of the proposition under consideration.

16. A Direct, Positive, or Affirmative Demonstration, is that which concludes with the direct and certain proof of the proposition in hand.--This kind of Demonstration is most satisfactory to the mind; for which reason it is called sometimes an Ostensive Demonstration.

17. An Indirect, or Negative Demonstration, is that which shows a proposition to be true, by proving that some absurdity would necessarily follow if the proposition advanced were false. This is also sometimes called Reductio ad Absurdum ; because it shows the absurdity and falsehood of all suppositions contrary to that contained in the proposition.

18. Method is the art of disposing a train of arguments in a proper order, to investigate either the truth or

falsity of a proposition, or to demonstrate it to others when it has been found out. This is either Analytical or Synthetical.

19. Analysis, or the Analytic Method, is the art or mode of finding out the truth of a proposition, by first supposing the thing to be done, and then reasoning back, step by step, till we arrive at some known truth.-- This is also called the Method of Invention, or Resolution ; and is that which is commonly used in Algebra.

20. Synthesis, or the Synthetic Method, is the searching out truth, by first laying down some simple and easy princi. ples, and pursuing the consequences flowing from them till we arrive at the conclusion.-This is also called the Method of Composition ; and is the reverse of the Analytic method, as this proceeds from known principles to an unknown conclusion; while the other goes in a retrograde order, from the thing sought, considered as if it were true, to some known principle or fact. And therefore, when any truth has been found out by the Analytic method, it may be demonstraled by a process in the contrary order, by Synthesis.

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ARITHMETIC.

ARITHI

RITHMETIC is the art or science of numbering ; being that branch of Mathematics which treats of the nature and properties of numbers. When it treats of whole numbers, it is called Vulgar, or Common Arithmetic ; but when of broken numbers, or parts of numbers, it is called Fractions.

Unity, or an Unir, is that by which every thing is called one ; being the beginning of number; as, one man, one ball, one gun.

Number is either simply one, or a compound of several units; as, one man, three men, ten men

An Integer, or Whole Number, is some certain precise quantity of units; as, one, three, ten. These are so called as distinguished from Fractions, which are broken numbers, or parts of numbers; as, one-half, two-thirds, or three-fourths.

NOTATION AND NUMERATION.

NOTATION, or NUMERATION, teaches to denote or express any proposed number, either by words or characters; or to read and write down any sum or number.

The numbers in Arithmetic are expressed by the following ten digits, or Arabic numera! figures, which were introduced into Europe by the Moors, about eight or nine hundred years since ; viz. I one, 2 two, 3 three, 4 four, 5 five, 6 six, 7 seven, 8 eight, 9 nine, O cipher, or nothing. These characters or figures were formerly all called by the general name of Ciphers; whence it came to pass that the art of Arithmetic was then often called Ciphering. Also the first nine are called Significant Figures, as distinguished from the cipher, which is of itself quite insignificant.

Besides this value of those figures, they have also another which depends on the place they stand in when joined together; as in the following table :

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