gibson:teaching:spring-2018:math445:lecture:arithmetic
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| Both sides previous revision Previous revision Next revision | Previous revision | ||
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gibson:teaching:spring-2018:math445:lecture:arithmetic [2018/01/23 13:45] gibson [Special numbers] |
gibson:teaching:spring-2018:math445:lecture:arithmetic [2018/01/24 18:05] (current) gibson [basic math functions] |
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| Line 78: | Line 78: | ||
| <code matlab> | <code matlab> | ||
| + | >> 1/0 | ||
| + | ans = | ||
| + | Inf | ||
| + | |||
| + | >> 0/0 | ||
| + | ans = | ||
| + | NaN | ||
| + | |||
| + | >> i^2 | ||
| + | ans = | ||
| + | -1 | ||
| + | | ||
| + | >> j^2 | ||
| + | ans = | ||
| + | -1 | ||
| + | | ||
| >> sin(pi) | >> sin(pi) | ||
| ans = | ans = | ||
| Line 91: | Line 107: | ||
| ans = | ans = | ||
| 2.7756e-17 % wha...? | 2.7756e-17 % wha...? | ||
| - | <code> | + | </code> |
| Here the issue is that computers use binary representations of numbers, not decimal representations. None of the three numbers 0.4, 0.3, and 0.1 can be represented exactly in binary. They're instead represented with binary fractions very nearly equal to 0.4, 0.3, and 0.1. Usually you don't see the difference, but sometimes, like here, you do. | Here the issue is that computers use binary representations of numbers, not decimal representations. None of the three numbers 0.4, 0.3, and 0.1 can be represented exactly in binary. They're instead represented with binary fractions very nearly equal to 0.4, 0.3, and 0.1. Usually you don't see the difference, but sometimes, like here, you do. | ||
| ====Variables==== | ====Variables==== | ||
| + | <code matlab> | ||
| >> x = 4 % assign value of 4 to variable x | >> x = 4 % assign value of 4 to variable x | ||
| x = | x = | ||
| Line 111: | Line 128: | ||
| ans = | ans = | ||
| 12 | 12 | ||
| + | </code> | ||
| ====Evaluating expressions==== | ====Evaluating expressions==== | ||
| + | |||
| + | If you want to evalue the same expression repeatedly with different variables, reset the value of the variables and use the arrow keys to "scroll up" to the expression. Then hit "enter" | ||
| + | |||
| + | <code matlab> | ||
| >> x = 3; | >> x = 3; | ||
| >> y = x^2 - 2*x + 5 | >> y = x^2 - 2*x + 5 | ||
| Line 122: | Line 143: | ||
| y = | y = | ||
| 4 | 4 | ||
| + | </code> | ||
| ==== basic math functions ==== | ==== basic math functions ==== | ||
| - | sin, cos, tan, sec, csc, cot, asin, acos, atan, | + | |
| - | exp, log, log10, abs, sqrt, factorial, mod | + | <code matlab> |
| + | sin, cos, tan, sec, csc, cot, asin, acos, atan % the classic trig funcs, in radians | ||
| + | sind, cosd, tand, secd, cscd, cotd, asind, acosd, atand % the classic trig funcs, in degrees | ||
| + | exp, log, log10, abs, sqrt, factorial, mod % other awesome functions | ||
| + | </code> | ||
| | | ||
| | | ||
gibson/teaching/spring-2018/math445/lecture/arithmetic.1516743901.txt.gz · Last modified: 2018/01/23 13:45 by gibson
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