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SCIENTIFIC POCKET
CALCULATOR Figure 1-32 illustrates a typical pocket calculator that replaces the slide rule, logarithm tables, and office adding machine. This tool, packed with the latest in state-of-the-art solid-state technology, is a great asset for our trade. With it we can handle many problems quickly and accurately without having to hassle with lengthy, tedious computations. This tool should serve us faithfully for a long time if we treat it with respect and care. Todays hand-held calculators have become an everyday part of our lives. Rugged and inexpensive, theyre a practical answer to the real need we all have for quick, accurate calculations. THE KEYBOARD Your calculator has many features to make calculations easy and accurate. To allow you to use all of these features without crowding the keyboard, the designer has caused some of the keys to have more than one function. If you look closely at the keyboard, youll notice that the keys in the column on the left side have two function symbols. These keys are called dual-function keys because they perform two functions. If you want to perform one of the first functions, simply press the key. To perform one of the second functions, youll need to press the 2nd key and then press the key for the function you wish to perform. INSTRUCTION MANUAL Every calculator on the market should have an instruction manual enclosed with it. Check out all the features and functions summarized in the instruction manual to become familiar with what your calculator will (and will not) do for you. HINTS ON COMPUTING It is a general rule that when you are expressing dimensions, you express all dimensions with the same precision. Suppose, for example, you have a triangle with sides 15.75, 19.30, and 11.20 ft long. It would be incorrect to express these as 15.75, 19.3, and 11.2 ft, even though the numerical values of 19.3 and 11.2 are the same as those of 19.30 and 11.20.It is another general rule that it is useless to work computations to a precision that is higher than that of the values applied in the computations. Suppose, for example, you are solving a right triangle for the length of side a, using the Pythagorean theorem. Side b is given as 16.5 ft, and side c, as 20.5 ft. By the theorem you know that side a equals the square root of (20.52 16.52), or the square root of 148.0. You could carry the square root of 148.0 to a large number of decimal places. However, any number beyond two decimal places to the right would be useless, and the second number would be determined only for the purpose of rounding off the first.The square root of 148.0, to two decimal places, is 12.16. As the 0.16 represents more than one-half of the difference between 0.10 and 0.20, you round off at 0.2, and call the length of side a 12.2 ft. If the hundredth digit had represented less than one-half of the difference between 0.10 and 0.20, you would have rounded off at the lower tenth digit, and called the length of side a 12.1 ft. Suppose that the hundredth digit had represented one-half of the difference between 0.10 and 0.20, as in 12.15. Some computers in a case of this kind always round off at the lower figure, as, 12.1. Others round off at the higher figure, as 12.2. Better balanced results are usually obtained by rounding off at the nearest even figure. By this rule, 12.25 would round off at 12.2, but 12.35 would round off at 12.4. |
 
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