Math Problem Statement

Use Newton's method to find the second and third approximation of a root of 5sin(x) = x, starting with x1 = 1 as the initial approximation.

Solution

We are tasked with using Newton's method to approximate the root of the equation:

5sin(x)=x5 \sin(x) = x

Newton's method uses the iterative formula:

xn+1=xnf(xn)f(xn)x_{n+1} = x_n - \frac{f(x_n)}{f'(x_n)}

where f(x)=5sin(x)xf(x) = 5 \sin(x) - x, and f(x)f'(x) is its derivative. Let's find the derivative of f(x)f(x):

f(x)=5cos(x)1f'(x) = 5 \cos(x) - 1

Given that the initial approximation is x1=1x_1 = 1, we will now calculate the second approximation x2x_2 and the third approximation x3x_3.

  1. Calculate f(x1)f(x_1) and f(x1)f'(x_1):

    • f(x1)=5sin(1)1f(x_1) = 5 \sin(1) - 1
    • f(x1)=5cos(1)1f'(x_1) = 5 \cos(1) - 1
  2. Apply Newton's method to get x2x_2: x2=x1f(x1)f(x1)x_2 = x_1 - \frac{f(x_1)}{f'(x_1)}

  3. Apply the same process to calculate x3x_3: x3=x2f(x2)f(x2)x_3 = x_2 - \frac{f(x_2)}{f'(x_2)}

Let me compute these approximations for you.Using Newton's method, the second and third approximations for the root of the equation 5sin(x)=x5 \sin(x) = x are:

  • The second approximation, x20.885x_2 \approx -0.885
  • The third approximation, x30.493x_3 \approx 0.493

Would you like more details or have any questions on the process?

Here are some related questions to explore further:

  1. How does Newton's method converge to a root?
  2. What are the advantages of Newton's method compared to other root-finding methods?
  3. Can Newton's method fail to converge? Under what conditions?
  4. How do we interpret the physical meaning of the equation 5sin(x)=x5 \sin(x) = x?
  5. How sensitive is Newton's method to the choice of the initial guess?

Tip: Always check the derivative when using Newton's method—if it's near zero, the method may fail due to division by very small numbers.

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Math Problem Analysis

Mathematical Concepts

Calculus
Numerical Methods
Root Finding

Formulas

Newton's iterative formula: x_(n+1) = x_n - f(x_n) / f'(x_n)
Function: f(x) = 5sin(x) - x
Derivative: f'(x) = 5cos(x) - 1

Theorems

Newton's Method for Root Approximation

Suitable Grade Level

College Level