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Fixed Point Iteration Calculator for Sin 3 Degrees Ti84

Reviewed by Calculator Editorial Team

Fixed point iteration is a numerical method for solving equations of the form x = g(x). This technique is particularly useful when calculating trigonometric functions like sin(3 degrees) on a TI-84 calculator. In this guide, we'll explain how to perform fixed point iteration for sin(3 degrees) using your TI-84 graphing calculator.

What is Fixed Point Iteration?

Fixed point iteration is a method for finding successively better approximations to the roots (or fixed points) of a function. The basic idea is to start with an initial guess and repeatedly apply a function to get closer to the solution.

The method works by defining a sequence where each term is obtained by applying a function g(x) to the previous term. The sequence converges to a fixed point if the function g(x) is a contraction mapping.

Fixed point iteration formula:

xn+1 = g(xn)

For trigonometric functions, we can use fixed point iteration to approximate values that might not be directly available on a calculator.

Calculating sin(3 degrees)

Calculating sin(3 degrees) directly on a TI-84 is straightforward, but understanding the fixed point iteration method provides insight into how such calculations are performed.

First, we need to convert degrees to radians since most calculators use radians for trigonometric functions. The conversion factor is π/180.

Degree to radian conversion:

3° × (π/180) ≈ 0.05236 radians

Once we have the angle in radians, we can use the sin function on the TI-84 calculator. However, if we wanted to implement this using fixed point iteration, we would need to define an appropriate function g(x).

TI-84 Instructions

To calculate sin(3 degrees) on your TI-84 calculator:

  1. Press the MODE key and ensure that the calculator is in degree mode (DEG).
  2. Press the 2ND key and then the SIN key to access the sin function.
  3. Enter the angle: 3.
  4. Press the ENTER key to get the result.

The TI-84 calculator will display sin(3°) ≈ 0.05233596.

If you need to perform fixed point iteration for sin(3 degrees), you would typically use a programming approach on the TI-84. Here's a simplified example of how you might set it up:

  1. Press the PRGM key and select NEW to create a new program.
  2. Name the program (e.g., SINITER).
  3. Enter the following code:
:0→A
:0→B
:While abs(A-B)>1E-6
:sin(3)→A
:sin(A)→B
:End
:Disp A

This program initializes two variables A and B, then iterates until the difference between them is very small, indicating convergence. The final value of A will be approximately sin(3 degrees).

Example Calculation

Let's walk through a simple example of fixed point iteration to approximate sin(3 degrees).

We'll use the function g(x) = sin(x) and start with an initial guess of x₀ = 0.05.

Iteration xₙ g(xₙ) = sin(xₙ)
0 0.05 sin(0.05) ≈ 0.049979
1 0.049979 sin(0.049979) ≈ 0.049959
2 0.049959 sin(0.049959) ≈ 0.049939
3 0.049939 sin(0.049939) ≈ 0.049919

After a few iterations, we can see that the values are converging toward approximately 0.05, which is close to the actual value of sin(3 degrees).

FAQ

What is the difference between fixed point iteration and Newton's method?
Fixed point iteration uses a function g(x) to generate a sequence that converges to a fixed point, while Newton's method uses the derivative of the function to find roots more quickly.
How many iterations are needed for accurate results?
The number of iterations required depends on the initial guess and the convergence rate. For most practical purposes, 5-10 iterations are sufficient for reasonable accuracy.
Can fixed point iteration be used for all trigonometric functions?
Fixed point iteration can be applied to any function that has a fixed point, but it may not always converge quickly or at all depending on the function and initial guess.
Why is sin(3 degrees) approximately 0.0523?
This is because 3 degrees is a small angle, and the sine of a small angle in radians is approximately equal to the angle itself (in radians).
How can I verify the result on my TI-84?
You can verify the result by using the built-in sin function on your TI-84 calculator and comparing it with the result obtained from fixed point iteration.