Convergence of Bisection Method

This proves that the Bisection Method converges linearly with K = 1/2.In summary, the Bisection Method is proven to converge linearly with a value of K = 1/2. This is shown by rearranging the given equation and taking the log of both sides, leading to the conclusion that p = 1 and therefore K = 1/2. This demonstrates that the Bisection Method is a linear operation, reducing the interval by 1/2 each time and converging on the real root.
  • #1
Adyssa
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Homework Statement



Show that the Bisection Method converges linearly with K = 1/2

Homework Equations



Note that x(sub n) converges to the exact root r with an order of convergence p if:

lim(n->oo) (|r - x(n + 1)|) / (|r - x(n)|^p) = lim(n->oo) (|e(n + 1)|) / (|e(n)|^p) = K

The Attempt at a Solution



EDIT: I can rearrange the equation above as follows (K = 1/2):

|e(n+1)| = 1/2|e(n)|^p

and I know that the bisection method is a linear operation, reducing the interval by 1/2 each time and converging on the real root, so p = 1, but I'm not sure how to show this?
 
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  • #2
EDIT: I think I've solved it.By rearranging the equation as above, we can show that p = 1 by taking the log of both sides:log(|e(n+1)|) = log(1/2|e(n)|^p)log(|e(n+1)|) = log(1/2) + plog(|e(n)|)dividing both sides by log(|e(n)|):log(|e(n+1)|)/log(|e(n)|) = log(1/2)/log(|e(n)|) + pSince the left side is always equal to 1, this means that p = 1 and therefore K = 1/2.
 

Related to Convergence of Bisection Method

What is the bisection method?

The bisection method is a numerical algorithm used to find the roots of a continuous function. It works by repeatedly dividing an interval in half and selecting the subinterval that contains a root. This process is continued until the root is found within a desired level of accuracy.

How does the bisection method ensure convergence?

The bisection method ensures convergence by always narrowing down the interval that contains a root. This is done by checking the sign of the function at the endpoints of the interval and determining in which subinterval the root must lie. This process is repeated until the root is found within the desired level of accuracy.

What is the convergence rate of the bisection method?

The convergence rate of the bisection method is linear, which means that the number of correct digits in the approximation of the root doubles with each iteration. This is slower compared to other methods such as the Newton-Raphson method which has a quadratic convergence rate.

What are the advantages of using the bisection method?

One advantage of using the bisection method is that it is relatively simple to implement and understand. It also has a guaranteed convergence to a root as long as the function is continuous and the initial interval contains a root. Additionally, it can handle functions with multiple roots within the same interval.

What are the limitations of the bisection method?

The bisection method can be slow compared to other root-finding methods, especially for functions with a steep slope near the root. It also requires the initial interval to be chosen carefully, as a poor choice can lead to slow convergence or no convergence at all. Furthermore, it is not suitable for finding complex roots or roots of functions with discontinuities.

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