16 MATHEMATICS 



MATHEMATICS 



FORMULAS 



The term formula, as used in mathematics and in techni- 

 cal books, may be defined as a rule in which symbols are used 

 instead of words; in fact, a formula may be regarded as a 

 shorthand method of expressing a rule. 



Most persons having no knowledge of algebra regard for- 

 mulas with distrust ; they think that a person must be a good 

 algebraic scholar in order to be able to use formulas. This 

 idea, however, is erroneous. As a rule, no knowledge of 

 any branch of mathematics except arithmetic is required to 

 enable one to use a formula. Any formula can be expressed 

 in words, and when so expressed it becomes a rule. 



Formulas are much more convenient than rules. They 

 show at a glance all the operations that are to be performed ; 

 they do not have to be read three or four times, as is the case 

 with most rules, to enable one to understand their meaning; 

 they take up less space, both in the printed book and in 

 one's notebook, than rules; in short, whenever a rule can 

 be expressed as a formula, the formula is to be preferred. 

 It is the intention in the following pages to show "how to 

 use such formulas as are likely to be encountered in "hand- 

 books," or other works of like nature. 



The signs used in formulas are the ordinary signs indica- 

 tive of operations and the signs of aggregation. All these 

 signs are used in arithmetic, but, to refresh the reader's 

 memory, their nature and uses will be explained before 

 proceeding further. 



The signs indicative of operations are six in number, viz.: 

 + , , X , -*- , ! , and V 



The sign ( + ) indicates addition, and is called plus; when 

 placed between two quantities, it indicates that the two 

 quantities are to be added. Thus, in the expression 25 + 17, 

 the sign ( + ) shows that 17 is to be added to 25. 



