SMA 330 • UNIT 2 • Mathematics
Polynomials And Interpolation
Topics covered: Lecture Objectives ………………………………………………………………………………………………………, Round-off and Truncation Errors ……………………………………………………………………………, Absolute and Relative Errors ……………………………………………………………………………………, Significant Figures ………………………………………………………………………………………………………, Propagation Errors ……………………………………………………………………………………………………… 1, General Formula for Propagated Error ………………………………………………………………, Self-test Questions ………………………………………………………………………………………………………, Further Reading …………………………………………………………………………………………………………
Verified Examination Problems
2 verified questions in catalogQuestion 2 (20 marks)
a) From the following data, estimate the value of $\int_{1}^{5} \log x \, dx$ using Simpson's 1/3 rule. Also obtain the value of $h$, so that the value of the integral will be accurate up to five decimal places.
| $x$ | 1.0 | 1.5 | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 4.5 | 5.0 |
|---|---|---|---|---|---|---|---|---|---|
| $y=\log x$ | 0.0000 | 0.4055 | 0.6931 | 0.9163 | 1.0986 | 1.2528 | 1.3863 | 1.504 | 1.6094 |
(8 marks)
(b) Determine the maximum step size that can be used in the tabulation of $f(x) = e^x$ in $[0, 1]$, so that the error in the linear interpolation will be less than $5 \times 10^{-4}$. Find also the step size if quadratic interpolation is used.
(8 Marks)
c) Evaluate the integral $I = \int_{0}^{1} \frac{x}{1+x^2} \, dx$ using trapezoidal rule with a subdivision of $0.25$. Estimate the maximum error involved.
(4 marks)
Question 1 (12 marks)
a) Define the following terms as used in computation
i) Relative Error
ii) Reformulation
iii) Interpolation [3 Marks]
b) i) Use three digit rounding arithmetic to perform the calculation below:
$$
\left( \frac{13}{14} - \frac{6}{14} \right) \div (2e - 5.4)
$$
ii) Compute the percentage error with the exact value determined to five digits rounding. [5 Marks]
c) Two qualities are found to be related as below
| (x_i) | 1.00 | 1.05 | 1.10 | 1.15 | 1.20 |
|---|---|---|---|---|---|
| (f(x_i)) | 1.0000 | 1.0240 | 1.0488 | 1.0724 | 1.0956 |
Assuming (y = f(x)) is continuous find
$$
\int_{1.0}^{1.2} f(x)dx, \text{ numerically using both trapezoidal and Simpsons rule.}
$$
[4 marks]
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