Page:Cowie's Printer's pocket-book and manual.djvu/74

66 be composed of several letters; for example, a + b ÷ c, instead of writing the quotient like a fraction.

involution. The character of involution.

 evolution. The character of evolution, or the extracting of roots.

⦢ or ⫍ are signs of majority; thus, a ⦢ b, expresses that a is greater than b.

∠ or ⫎ are signs of minority; when we would denote that a is less than b.

∽ is the character of similitude used by Wolfius, Leibnitz, and others: it is used in other authors for the difference between two quantities, while it is unknown which is the greater of the two.

∷ so is. The mark of geometrical proportion disjunct, and is usually placed between two pair of equal ratios, as 3:6 ∷ 4:8, shews that 3 is to 6 as 4 is to 8.

∶ or ∴ is an arithmetical equal proportion; as 7.3:13.9; i.e. 7 is more than 3, as 13 is more than 9.

□ Quadrat, or regular quadrangle as follows, □ AB = □ BC; i.e. the quadrangle upon the line AB is equal to the quadrangle upon the line BC.

∆ Triangle; as, ∆ABC = ∆ADC.

∠ an Angle; as, ∠ABC = ∠ADC.

⊥ Perpendicular; as, AB ⊥ BC.

▭ Rectangled Parallelogram; or the product of two lines.

∥ The character of parallelism.

≚ equiangular, or similar.

$$\stackrel{|}{=}$$ equilateral.

∟ right angle.

° denotes a degree; thus 45° implies 45 degrees.

′ a minute; thus, 50′ is 50 minutes: ″, ‴, ⁗, denote seconds, thirds, and fourths: and the same characters are used where the progressions are by tens, as it is here by sixties.