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Published byAlfred Cox Modified over 9 years ago
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Lecture 19 – Numerical Integration 1 Area under curve led to Riemann sum which led to FTC. But not every function has a closed-form antiderivative.
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2 Using rectangles based on the left endpoint of each subinterval. Using rectangles based on the right endpoints of each subinterval ab ab
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3 Using rectangles based on the midpoint of each subinterval. ab
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4 Regardless of what determines height:
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5 Example 1 Use the midpoint rule to estimate the area from 0 to 120. 120 2 4 6 8
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Example 2 Compare the three rectangle methods in estimating area from x = 1 to 9 using 4 subintervals. 6 f(x) x 19 12 34 56 7 89
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Lecture 20 – More Numerical Integration 7 Instead of rectangles, look at other types easy to compute. Trapezoid Rule: average of Left and Right estimates Area for one trapezoid is (average length of parallel sides) times (width). ababab
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Trapezoid Rule is the average of the left and right estimates, so 8 x0x0 x1x1 x n-1 x2x2 xnxn
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9 Simpson’s Rule: weighted average of Mid and Trap estimates a – must break into even number of subintervals – areas under quadratic curves – pairs of subintervals form quadratic function b
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Simpson’s Rule is the sum of these areas, so 10 Calculate efficiency of estimates with absolute errors, relative errors, and percent error (change decimal of relative to %).
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11 Example 3 Use the trapezoid and Simpson’s rules to estimate the integral. 9 1
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12 Example 4 Use the M 6, T 6, and S 6 to fill in the table for the given integral. 8 2 RuleEstimateAbsolute Error Relative Error M6M6 T6T6 S6S6
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