Solving 10 Sin x = -x: Tips & Ideas

  • Context: High School 
  • Thread starter Thread starter kelvintc
  • Start date Start date
  • Tags Tags
    Ideas Sin Tips
Click For Summary

Discussion Overview

The discussion revolves around the equation 10 sin x = -x, focusing on methods for solving this transcendental equation. Participants explore various approaches, including numerical methods and graphical interpretations, while also addressing the challenges of finding solutions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant requests tips for solving the equation and expresses frustration at not knowing how to transform it.
  • Another participant identifies the equation as transcendental and suggests that solutions may involve finding intercepts between trigonometric and non-linear functions.
  • A participant mentions that x=0 is an obvious solution and suggests using Newton's method for finding additional solutions.
  • It is noted that there are three roots to the equation, with x=0 being one, and that the other two roots may require numerical estimation.
  • A participant expresses a lack of knowledge about Newton's method and the concept of finding intercepts, indicating they have not yet learned these topics.
  • Newton's method is described as a technique for refining guesses based on deviations, but it is suggested that knowledge of calculus is necessary to apply it effectively.
  • One participant provides the five solutions to the equation with high precision, including both positive and negative roots.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the methods for solving the equation, with multiple approaches and suggestions presented. There is acknowledgment of the existence of multiple roots, but the discussion remains unresolved regarding the best method to find all solutions.

Contextual Notes

Participants express uncertainty about the applicability of various methods due to their current level of knowledge, particularly regarding calculus and numerical methods. The discussion reflects a range of familiarity with the mathematical concepts involved.

Who May Find This Useful

This discussion may be useful for students learning about transcendental equations, numerical methods, and those seeking to understand different approaches to solving complex mathematical problems.

kelvintc
Messages
38
Reaction score
0
10 sin x = -x
can anyone give me tips how to solve this equation?
i run out of ideas even to transform this equation to another form.. sigh sigh

thanks...
 
Mathematics news on Phys.org
It seems you have a transcendental equation0--i don't think those are solvable, unless you know how to find intercepts between trig and non-vertical/non-horizontal functions.
 
x=0

Or do you want more solutions? Then look up Newton's method.
 
there are 3 roots in this equation. 0 is the obvious one, the other two needs to estimate by computer.
 
oh ... thanks...
p/s : (1) what's Newton method?
(2) find intercepts between trig and non-vertical/non-horizontal functions ?

i not yet learn both also and my textbook is doesnot contain Newton's method also.. i will try to find it out...
my friend told me use 'trials and errors' method, is it applicable ?
thanks
 
Newton's method is a clever way of correcting your guess by using the deviation. But you need to know some calculus, and I don't think you know any. In any case, if x_n is your n^th trial, then you find your next trial as follows:
[tex]x_{n+1}=x_n-{10\sin x_n+x_n\over 10\cos x_n +1}[/tex]
Of corse, with more than one root to 10sin x+x=0, you'll need an appropriate initial guess or you'll just keep going back to a known solution like x=0.
 
here are the 5 solutions to 50 digits...
0
+/- 3.49906381990775821737274462727340586713040476067
+/- 5.67920779631440367042018458778408009777615397061
 
oh .. thanks a lot ... :)
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
4K
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 70 ·
3
Replies
70
Views
8K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 22 ·
Replies
22
Views
3K
  • · Replies 13 ·
Replies
13
Views
4K
  • · Replies 4 ·
Replies
4
Views
2K