4. A certain computer algorithm used to solve very complicated differential equations uses an iterative method. That is, the algorithm solves the problem the first time very approximately, and then uses that first solution to help it solve the problem a second time just a little bit better, and then uses that second solution to help it solve the problem a third time just a little bit better, and so on. Unfortunately, each iteration (each new problem solved by using the previous solution) takes a progressively longer amount of time. In fact, the amount of time it takes to process the $k$-th iteration is given by $T(k) = 1.2^k + 1$ seconds. A. Use a definite integral to approximate the time (in hours) it will take the computer algorithm to run through 60 iterations. (Note that $T(k)$ is the amount of time it takes to process just the $k$-th iteration.) Explain your reasoning. B. The maximum error in the computer's solution after $k$ iterations is given by $Error = 2k^{-2}$. Approximately how long (in hours) will it take the computer to process enough iterations to reduce the maximum error to below 0.0001?
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We can do this by summing up the time it takes for each iteration from k=1 to k=60. Since T(k) = 1.24^k seconds, we can write the total time as: $$ T_{total} = \sum_{k=1}^{60} T(k) = \sum_{k=1}^{60} 1.24^k \text{ seconds} $$ To approximate this sum, we can use a Show more…
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(a) Use Euler's method with each of the following step sizes to estimate the value of $ y(0.4), $ where $ y $ is the solution of the initial-value problem $ y' = y, y(0) = 1. $ (i) $ h = 0.4 $ (ii) $ h = 0.2 $ (iii) $ h = 0.1 $ (b) We know that the exact solution of the initial-value problem in part (a) is $ y = e^x. $ Draw, as accurately as you can, the graph of $ y = e^x, 0 \le x \le 0.4, $ together with the Euler approximations using the step sizes in part (a). (Your sketches should resemble Figure 12, 13, and 14.) Use your sketches to decide whether your estimates in part (a) are underestimates or overestimates. (c) The error in Euler's method is the difference between the exact value and the approximate value. Find the errors made in part (a) in using Euler's method to estimate the true value of $ y(0.4), $ namely $ e^{0.4}. $ What happens to the errors each time the steps size is halved?
Differential Equations
Direction Fields and Euler's Method
(a) Use Euler's method with each of the following step sizes to estimate the value of $y(0.4),$ where $y$ is the solution of the initial-value problem $y^{\prime}=y, y(0)=1 .$ (i) $h=0.4 \quad$ (ii) $h=0.2 \quad$ (iii) $h=0.1$ (b) We know that the exact solution of the initial-value problem in part (a) is $y=e^{x} .$ Draw, as accurately as you can, the graph of $y=e^{x}, 0 \leqslant x \leqslant 0.4,$ together with the Euler approximations using the step sizes in part (a).(Your sketches should resemble Figures $12,$ i3, and $14 .$ .) Use your skethes to decide whether your estimates in part (a) are underestimates or overestimates. (c) The error in Euler's method is the difference between the exact value and the approximate value. Find the errors made in part (a) in using Euler's method to estimate the true value of $y(0.4),$ namely $e^{0.4} .$ What happens to the error each time the step size is halved?
Problem 1: Consider the following Initial Value Problem (IVP) where y is the dependent variable and t is the independent variable: y' = sin(t) * (1 - y) with y(0) = y_0 and t >= 0 Note: the analytic solution for this IVP is: y(t) = 1 + (y_0 - 1)e^(cos(t)-1) Part 1A: Approximate the solution to the IVP using Euler's method with the following conditions: Initial condition y_0 = -1/2; time step h = 1/16; and time interval t in [0,20] + Derive the recursive formula for Euler's method applied to this IVP + Plot the Euler's method approximation + Plot the absolute error between the approximation and the exact solution using a semilog plot Part 1B: Approximate the solution to the IVP using the Improved Euler's method with the following conditions: Initial condition y_0 = -1/2; time step h = 1/16; and time interval t in [0,20] + Derive the recursive formula for the Improved Euler's method applied to this IVP + Plot the Improved Euler's method approximation + Plot the absolute error between the approximation and the exact solution using a semilog plot Part 1C: Approximate the solution to the IVP using the RK4 method with the following conditions: Initial condition y_0 = -1/2; time step h = 1/16; and time interval t in [0,20] + Plot the RK4 method approximation + Plot the absolute error between the approximation and the exact solution using a semilog plot
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