The Computable Differential Equation Lecture ... - Bruce E. Shapiro
The Computable Differential Equation Lecture ... - Bruce E. Shapiro
The Computable Differential Equation Lecture ... - Bruce E. Shapiro
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46 CHAPTER 3. APPROXIMATE SOLUTIONS<br />
y 3 = y 2 + hf(t 2 , y 2 ) (3.26)<br />
= 1.5625 + (0.25)(1.5625) = 1.953125 (3.27)<br />
t 3 = t 2 + h = 0.5 + 0.25 = 0.75 (3.28)<br />
(t 3 , y 3 ) = (0.75, 1.953125) (3.29)<br />
y 4 = y 3 + hf(t 3 , y 3 ) (3.30)<br />
= 1.953125 + (0.25)(1.953125) = 2.44140625 (3.31)<br />
t 4 = t 3 + 0.25 = 1.0 (3.32)<br />
(t 4 , y 4 ) = (1.0, 2.44140625) (3.33)<br />
Since t 4 = 1 we are done. <strong>The</strong> solutions are tabulated in table 3.1 for this and<br />
other step sizes. <strong>The</strong>se solutions are also illustrated in figure 3.1. <strong>The</strong> green dots in<br />
the figure correspond to the numbers calculated here; the other colors correspond<br />
to other step sizes. <strong>The</strong> points are joined by straight lines in the figure, but the<br />
straight lines are not part of the solution, only the dots. <strong>The</strong> figure also shows the<br />
exact solution.<br />
Table 3.1: Approximate values for different step sizes. See example 3.1.<br />
t h = 1/2 h = 1/4 h = 1/8 h = 1/16 exact solution<br />
0.0000 1.0000 1.0000 1.0000 1.0000 1.0000<br />
0.0625 1.0625 1.0645<br />
0.1250 1.1250 1.1289 1.1331<br />
0.1875 1.1995 1.2062<br />
0.2500 1.2500 1.2656 1.2744 1.2840<br />
0.3125 1.3541 1.3668<br />
0.3750 1.4238 1.4387 1.4550<br />
0.4375 1.5286 1.5488<br />
0.5000 1.5000 1.5625 1.6018 1.6242 1.6487<br />
0.5625 1.7257 1.7551<br />
0.6250 1.8020 1.8335 1.8682<br />
0.6875 1.9481 1.9887<br />
0.7500 1.9531 2.0273 2.0699 2.1170<br />
0.8125 2.1993 2.2535<br />
0.8750 2.2807 2.3367 2.3989<br />
0.9375 2.4828 2.5536<br />
1.0000 2.2500 2.4414 2.5658 2.6379 2.7183<br />
Math 582B, Spring 2007<br />
California State University Northridge<br />
c○2007, B.E.<strong>Shapiro</strong><br />
Last revised: May 23, 2007