Math Problem Statement

Calculate two iterations of Newton's Method to approximate a zero of the function f(x) = cos(x) using the initial guess x1 = 1.1. Round your answers to four decimal places.

Solution

The problem in the image involves using Newton's Method to approximate the root of the function f(x)=cos(x)f(x) = \cos(x) with an initial guess of x1=1.1x_1 = 1.1.

Newton's Method formula is given by: xn+1=xnf(xn)f(xn)x_{n+1} = x_n - \frac{f(x_n)}{f'(x_n)} where:

  • f(xn)=cos(xn)f(x_n) = \cos(x_n)
  • f(xn)=sin(xn)f'(x_n) = -\sin(x_n)

First iteration n=1n = 1:

Given:

  • x1=1.1x_1 = 1.1
  1. Compute f(x1)=cos(1.1)f(x_1) = \cos(1.1): f(x1)=cos(1.1)0.4536f(x_1) = \cos(1.1) \approx 0.4536 (This value is correct as per the image.)

  2. Compute f(x1)=sin(1.1)f'(x_1) = -\sin(1.1): f(x1)=sin(1.1)0.8912f'(x_1) = -\sin(1.1) \approx -0.8912 (This value is correct as well.)

  3. Now, calculate the Newton's Method formula: x2=1.10.45360.89121.6095x_2 = 1.1 - \frac{0.4536}{-0.8912} \approx 1.6095 This step also matches the image.

Second iteration n=2n = 2:

Now, using x2=1.6095x_2 = 1.6095:

  1. Compute f(x2)=cos(1.6095)f(x_2) = \cos(1.6095): f(x2)=cos(1.6095)0.0001f(x_2) = \cos(1.6095) \approx -0.0001 (This value is rounded correctly.)

  2. Compute f(x2)=sin(1.6095)f'(x_2) = -\sin(1.6095): f(x2)=sin(1.6095)0.9999f'(x_2) = -\sin(1.6095) \approx -0.9999 (This value is also correct.)

  3. Now, apply Newton's Method again: x3=1.60950.00010.99991.6096x_3 = 1.6095 - \frac{-0.0001}{-0.9999} \approx 1.6096 This matches the calculation in the table as well.

Corrections:

The values calculated for f(xn)f(x_n), f(xn)f'(x_n), and f(xn)f(xn)\frac{f(x_n)}{f'(x_n)} in the image are mostly correct, but some entries like the second xnx_n values (for iteration 2) are slightly off due to rounding.

Let me know if you'd like further clarifications or have any questions. Here are five questions that follow:

  1. How does Newton's Method converge to a root?
  2. What is the significance of the derivative f(x)f'(x) in Newton's Method?
  3. What would happen if f(xn)=0f'(x_n) = 0 during an iteration?
  4. Why is the initial guess important in Newton's Method?
  5. Can Newton's Method fail to converge? Under what conditions?

Tip: Newton's Method generally converges faster when the initial guess is closer to the actual root.

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Math Problem Analysis

Mathematical Concepts

Newton's Method
Calculus
Derivatives
Trigonometric Functions

Formulas

Newton's Method formula: x_{n+1} = x_n - f(x_n) / f'(x_n)
f(x) = cos(x)
f'(x) = -sin(x)

Theorems

Newton's Method for finding roots

Suitable Grade Level

University Level (Calculus and Numerical Methods)