USE OF THE SCIENTIFIC CALCULATOR A scientific calculator is an invaluable tool that is an indispensable part of your problemsolving strategy. To take full advantage of your calculator, it is essential that you can use it with confidence. This confidence comes from an understanding of the steps involved in setting up and solving a problem and confidence grows with practice. This Appendix is designed to provide examples of the most commonly encountered calculations coupled with exercises intended to help you build confidence. This Appendix is not meant to be a substitute for, but rather, a supplement to the information supplied in the instruction manual for your particular calculator. The instructions provided below will work for most but not all makes of calculators. Especially for Graphics Calculators (such as TI 82, TI 83, TI 85), you may be able to accomplish the same result with a different combination of keystrokes. 1. Entering Exponents To enter an exponent, you need to use the key labeled EE , EX , or EXP . Look for this key. For simplicity, EXP (for exponential) is used in the entire exercise. Example: To enter 3 x 10^{4}, press 3 EXP 4. Display: 3 ^{04} or 3 04 [This does NOT mean 3 to 4^{th} power, but 3x10^{4} or 30,000!] NOTE: It is a common mistake to enter it as 3 X 10 EXP 4, which would represent 3 x 10^{5} instead, as you had told the calculator to do 3 x 10 x 10 ^{4} ! 2. Entering Negative Numbers To enter a negative number, use the key labeled +/ CHS. For simplicity +/ will be used here. (Be careful not to press the key for subtraction. You only want to change the sign to negative.) For Graphics Calculators, negative numbers are entered by pressing (–) before pressing the number. For example, to enter –3, press (–) 3. Example: To enter 3 x 10 ^{}^{ 4}, press 3 EXP 4 +/.
Display: 3 ^{}^{ 04 }or 3 04 ^{ }Example:
^{ }
To enter 3 x 10 ^{4}, press 3 +/ EXP 4.
Display: 3 ^{04} or 3 04
3. Multiplying and Dividing Numbers in Exponential Form Example: Calculate (3x10^{4}) (2x10^{3}). Press 3 EXP 4 X 2 EXP 3 =
ans. 6x10^{7}
Practice: Calculate ( 4.827x10^{6})(2.17x10^{}^{ 4}).
ans. 1047.459
or 1.047459 x 10^{3}
(Record as 1.05 x 10^{3})
If you didn’t get this answer, try: 4.827 +/ EXP 6 X 2.17 EXP 4 +/ = Practice: Calculate (3.89x10^{2})(3.7x10 ^{}^{ 4})
(2.1 x 10^{3})(1.64x10^{}^{ 6})
ans. 41.791521 (Record as 42) If you didn’t get this answer, try: 3.89 EXP 2 X 3.7 EXP 4 +/ 2.1 EXP 3 1.64 EXP 6 +/ = Practice: Calculate 10^{3} x 10^{4} ans. 10^{7}
^{ }
If you didn’t get this answer, try: 1 EXP 3 X 1 EXP 4 = Practice: 10 ^{8} x 10 ^{2} ans. 10^{ 16}
10 ^{}^{ 6} ^{ }If you didn’t get this answer, try: 1 EXP 8 X 1 EXP 2 1 EXP 6 +/ =
4. Order of Operations The calculator will perform these functions in this order: 1) powers and roots (such as squares and square roots); 2) functions within parentheses; 3) x and ; 4) + and .
Problem:
3 x 6 ans. 3
2 + 4 If you didn’t get this answer, try: 3 X 6 ( 2 + 4 ) = If you simply did 3 X 6 2 + 4 = , you will get the erroneous answer of 13, because you have actually told the calculator to perform + 4. The calculator performed “2” before “+4”. Problem: 3 + 7 ans. 0.5
4 x 5 If you didn’t get this answer, try: ( 3 + 7 ) 4 5 = . You press 5 rather than X 5 because 5 is in the denominator and so you want to divide by 5.
Note: It is a common mistake to do 3 + 7 4 X 5, which gives you the erroneous answer of 11.75 or 12.5, depending on the model of your calculator. You have actually told the calculator to perform 3 + x 5 instead!
If you have trouble remembering the order of operations, you might want to routinely write in parentheses for the numerator and for the denominator: Problem: 3 x 6 ans. 0.9
4 x 5 Problem: (3 7) (4 + 6 ) ans. 8
(2 + 3) Problem: 3 x 4 ans. 1.9285714
7 x 8/9 Problem:
Calculate 0.000 000 000 25 x 12345678999 ans. 3.1 (Graphics calculators give 3.08641975, which should then be recorded as 3.1) Note: Unless you have a graphics calculator, you probably cannot enter this many digits. The solution is to express your number in scientific notation and/or round off to a more manageable number of digits. In this example, 0.000 000 000 25 must be entered as 2.5x10^{}^{10} and 12345678999 entered as 1.23x10^{10} to give 3.075 which is rounded to 3.1. (Rules on significant figures and rounding off numbers are covered elsewhere. 5. Interconvert between nonexponential mode and scientific mode You can do this in your head, but here is how your calculator can reliably perform this function: Enter 187.85. Can you convert the display to show 1.8785x10^{2} ? Your calculator most likely uses one of the following procedures for the interconversion: TI 81 , TI 82 , TI 83: Press Mode , use to highlight NORM or SCI on display
Press ENTER Press CLR or EXIT to return to regular screen
Enter the number then press ENTER
You could enter the number first, then do the steps described above. Casio fx 250: Mode 9 is normal (nonexponential), Mode 8 is scientific notation Use Mode 8 9 to show scientific notation with 9 digits. Display: 1.87850000x10^{2}
Use Mode 8 2 to show scientific notation with 2 digits. Display: 1.9 x 10^{2}
_{ }Use Mode 9 to return to nonexponential form. Display: 187.85 other Casios: Mode 1 is FIX Mode 2 is SCI Mode 3 is NORM Use Mode 2 9 to show scientific notation with 9 digits.
Use Mode 3 1 to show nonexponential which automatically switches to sci. notation when the number is less than .01
Use Mode 3 1 to show nonexponential which automatically switches to sci. notation when number is less than . 000001
TI 25x: Press X 1 EE (to switch to scientific notation) Press 2^{nd} EE (to switch back to nonexponential form) Sharp, & some others: INV EE (converts numbers to nonexponential form)
1 X EE converts numbers to scientific notation
Certain models: Use 2^{nd} F and FSE where F or FD means floating decimal. (normal display)
S or SCI means scientific notation E means engineering
6. Log and Antilog To find the log of a number you simply enter the number and then press LOG.
To find the antilog of a number you enter the number and then press the 10^{x} key. Usually this is the second function of the same key you used for LOG. In most calculators, the label for 10^{x} appears above the key for LOG. To access that function you press the INV or SHIFT or 2^{nd} key (depending on what brand of calculator you have) before pressing LOG. Note: It will be useful to review the rules for treatment of significant figures when using logarithms. They are briefly summarized at the end of this Appendix. Problem: log 5 ans. 0.69897 (recorded as 0.7; one significant figure) Problem: antilog 5 ans. 100000 or 10^{5} Problem: log 5.2x10^{–3} ans. –2.2839967 (recorded as –2.28; 3 significant figures)
Note:If you get an error message you probably did not enter the number in the proper format.
You should enter it as 5.2 EXP –3 LOG rather than 5.2 x 10 ^ –3 LOG because the calculator is going to calculate log of –3, which is impossible because you cannot calculate the log of a negative number. By entering 5.2 EXP –3, the calculator is treating it as ONE number (5.2x10^{–3}). By entering 5.2 x 10 ^ –3, the calculator is treating it as TWO numbers that you want multiplied: 5.2 and 10^{–3}. When you press LOG, your calculator “thinks” you want the log of the last number (–3).
Problem: log ans. 4.284430734… (recorded as 4.284; 4 significant figures) If you didn’t get this answer try: ( 3.85 EXP 4 2.00 ) LOG
or 3.85 EXP 4 2.00 = LOG (You need to complete the division before pressing the LOG key. If you pressed the keys in this order: 3.85 EXP 4 2.00 LOG, you are asking the calculator to calculate only the log of 2.00 ) Problem: antilog 7.2 x 10^{ –2} ans. 1.18
Try this: 7.2 EXP 2 +/–^{ } 10 ^{x}
7. Natural log (ln) and antinatural log (antiln)
Natural logarithms follow the same rules as base 10 logarithms. Use ln for natural log and the e^{x} key for antinatural log. Again, e^{x} is usually the second function of the same key you used for ln, to be accessed by pressing the INV, SHIFT, or 2^{nd} key first. Problem: ln 3.2 ans. 1.1631508 (recorded as 1.16) Problem: antiln 1.2x10^{–3} ans. 1.0012007 (recorded as 1.001)
(Remember to enter the number as 1.2 EXP –3.)
Rules for handling significant figures for log, antilog, ln and antiln:
When you find the log of a number, the number of significant figures of that number is the number of decimal places of the answer. Example 1: log 5.1 = ? Ans. 0.71
5.1 has 2 significant figures: answer 0.707570 should be rounded to 2 decimal places.
Example 2: log 0.0327 = ? Ans. –1.485
0.0327 has 3 significant figures; –1.4854 should be rounded to 3 decimal places.
Example 3: log 2x10^{–2} = ? Ans. –1.7
2x10^{–2} has 1 significant figure; –1.6989 should be rounded to 1 decimal place. When you find the antilog of a number, the number of decimal places of that number in NONEXPONENTIAL FORM is the number of significant figures of the answer. Example 4: antilog 3.2x10^{–2} = ?
You must first convert 3.2x10^{–2} to nonexponential form: 0.032
0.032 has 3 decimal places; the answer 1.076465 should be rounded to 1.08 (3 sig. fig.) Significant figures for ln and antiln work the same way:
Example 5: ln 7.5 = 2.01 (7.5 has 2 significant figures; the answer should have 2 decimal places.)
Example 6: antiln 2.7x10^{–1} = 1.3 (2.7x10^{–1} = 0.27 has 2 decimal places; the answer has 2 significant figures.
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