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Unformatted text preview: 1 Linear interpolation 1.1 Description Linear interpolation is a way to fill in the “holes” in tables. As an example, if you want to find the saturated pressure of water at a temperature of 40 ◦ C you can look in Table B.1.1, (p.674), for 40 ◦ C in the first column. The corresponding desired pressure is then in the next column; in this case, 7.384 kPa. But what if you want to find the saturated pressure at 38 ◦ C instead of 40 ◦ C? A temperature of 38 ◦ C is not in the table. You could of course just ignore the difference between 38 ◦ C and 40 ◦ C, and still take the saturated pressure to be 7.384 kPa. But that is not acceptable in this class; it is too inaccurate. To get an accurate value, you must use linear interpolation. (Though taking the closest value, 40 ◦ C, is of course better than nothing in case you forgot how to do linear interpolation during an exam.) Let’s introduce a few symbols. Let g be your given value, 38 ◦ C in this example. Let g 1 and g 2 be the two closest approximations to g in the table. A look at Table B.1.1 shows that the two closest values you can find in the table are 35...
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- Spring '09
- 5.628 kPa, 7.384 kPa, 1.3 20 kPa, 6.682 kPa