SYMBOLS AND ABBREVIATIONS.
∴ expresses the word therefore.
∵ . . . . . . . . . . . . . . . . because.
= . . . . . . . . . . . . . . . . equal. This sign of equality may be read equal to, or is equal to, or are equal to; but any discrepancy in regard to the introduction of the auxiliary verbs is, are, &c. cannot affect the geometrical rigour.
≠ means the same as if the words 'not equal' were written.
> signifies greater than.
< . . . . . . less than.
≯ . . . . . . not greater than.
≮ . . . . . . not less than.
+ is read plus (more), the sign of addition; when interposed between two or more magnitudes, signifies their sum.
− is read minus (less), signifies subtraction; and when placed between two quantities denotes that the latter is to be taken from the former.
× this sign expresses the product of two or more numbers when placed between them in arithmetic and algebra; but in geometry it is generally used to express a rectangle, when placed between "two straight lines which contain one of its right angles." A rectangle may also be represented by placing a point between two of its conterminous sides.
: :: : expresses an analogy or proportion; thus, if A, B, C and D, represent four magnitudes, and A has to B the same ratio that C has to D, the proposition is thus briefly written,
,
or .
This equality or sameness of ratio is read,
