How Does Sketching Graphs Help Find the Real Root of f(x) = 2sin(x) - 3x + 2?

In summary, by sketching the graphs of y = 2sin(x) and y = 3x - 2 and finding their intersection point, we can see that the function f(x) = 2sin(x) - 3x + 2 has only one real root. This root can be used in the Newton-Raphson method to find a more precise solution. Additionally, it is important to note that a function has zeroes, not roots.
  • #1
Bucky
82
0
"By sketching appropriate graphs (one of them a straight line) show that the function
f(x) = 2sin(x) - 3x + 2

has only one real root."

this one confuses me from the word go. how can you sketch a straight line of that function when it has sin as part of it?
 
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  • #2
The problem did say "graphs" (plural).
How about y= 2 sin(x) and y= 3x- 2?

Where the graphs cross, 2 sin(x)= 3x- 2 so 3 sin(x)- 3x+ 2= 0.

(In the interest of beating a dead horse)
Was that the exact wording of the problem? A function does not have "roots". A function has "zeroes", which are "roots" of the equation f(x)= 0.

If I saw something like "find the roots of f(x)= x2" I would think "x2= 1 or x2= 4 or x2= 1000...?"
 
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  • #3
yeah that's a word for word quote.

ok so i set the two functions up and compared them and they cross once at approx 1.3, 1.9

i thought that the 1.3 was the value that has to be used in the Newton rhapson method, but the first iteration derivates so heavily from the origonal (i ended up with -0.49908) that i think I am wrong.

EDIT: Yeah somethings wrong...the more iterations i do the more the number jumps around.

DOUBLE EDIT: Calculator was in wrong mode, I am an idiot.
 
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  • #4
DOUBLE EDIT: Calculator was in wrong mode, I am an idiot.
Well, I wasn't going to mention it---
 

Related to How Does Sketching Graphs Help Find the Real Root of f(x) = 2sin(x) - 3x + 2?

1. What is the Newton-Rhapson method?

The Newton-Rhapson method is an iterative mathematical algorithm used to find the roots of a given function. It is based on the idea of repeatedly approximating the root of a function by using the slope of the function at a given point.

2. How does the Newton-Rhapson method work?

The Newton-Rhapson method starts with an initial guess for the root of the function. It then uses the derivative of the function at that point to find a new, more accurate guess for the root. This process is repeated until the desired level of accuracy is achieved.

3. What are the advantages of using the Newton-Rhapson method?

The Newton-Rhapson method is known for its fast convergence rate, meaning it can find the root of a function with high accuracy in a relatively small number of iterations. It is also a versatile method that can be applied to a wide range of functions.

4. What is the importance of graph sketching in the Newton-Rhapson method?

Graph sketching is an important step in the Newton-Rhapson method as it helps to visualize the behavior of the function and identify potential roots. By plotting the function and its derivative, it becomes easier to choose a suitable initial guess for the root and track the convergence of the algorithm.

5. Can the Newton-Rhapson method fail?

Yes, the Newton-Rhapson method can fail to find the root of a function in certain cases. This can happen if the initial guess is too far from the actual root, if the function has multiple roots, or if the function is too complex for the method to handle. It is important to carefully choose the initial guess and monitor the convergence of the algorithm to avoid such failures.

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