Why is it impossible to solve y explicitly in this equation?

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Discussion Overview

The discussion revolves around the equation $$y + \sin y = x$$ and the challenges associated with solving for y explicitly. Participants explore methods for graphing the function and the implications of the transcendental nature of trigonometric functions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants question how to graph the function without an explicit solution for y.
  • One suggestion is to create a table of values by selecting y-values and solving for x.
  • Another participant points out that the presence of the sine function makes the equation transcendental, complicating algebraic solutions.
  • It is noted that while one cannot solve $$\sin y = x$$ algebraically, an inverse sine function is used, suggesting a similar approach could be applied to the original equation.
  • Another viewpoint suggests that while a closed form solution may not exist, numerical methods could be employed to find solutions as long as certain conditions are met.
  • A participant introduces the explicit function theorem as a potential method to explore local solutions for y.
  • One participant proposes graphing $$y = x + \sin(x)$$ and then flipping the axes to visualize the relationship.

Areas of Agreement / Disagreement

Participants express a general agreement on the challenges posed by the transcendental nature of the sine function, but there are differing opinions on the feasibility of finding solutions and the methods to graph the function.

Contextual Notes

Some participants mention the limitations of algebraic methods for transcendental equations and the potential for numerical solutions, but the discussion does not resolve these complexities.

Who May Find This Useful

This discussion may be of interest to those studying mathematical functions, particularly in the context of transcendental equations and graphing techniques.

InvalidID
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$$y+siny=x$$

How would you even graph a function like this if you can't solve for y explicitly?
 
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InvalidID said:
$$y+siny=x$$

How would you even graph a function like this if you can't solve for y explicitly?
Make a table of values. Pick some y-values and solve each of them for x.
 
Why is it impossible to solve y explicitly in this equation?
 
The presence of sin y. Trig functions are transcendental and cannot be solved using algebraic methods alone.
 
SteamKing said:
The presence of sin y. Trig functions are transcendental and cannot be solved using algebraic methods alone.

With this in mind (and I agree) one cannot solve this either,
\sin{y} = x
We have to invent a special function, the inverse sine, to solve it. By that same logic, we can invent a special function to solve the original equation. But it would be no more "solved" than using the inverse sine function to solve my equation above.
 
you can graph x as a function of y explicitly, then turn the graph by 90° and flip (mirror image) the rotated graph.

i do not think there is a closed form solution to

y + a \sin(y) = x

but you can still solve it numerically, as long as |a| \le 1. there are places in the y=f(x) function where the slope is infinite, but only on a single point. sort of like the real function y = x^{1/3}.
 
Have you tried to apply the explicit function theorem to see if a local solution for y is
possible?
 
InvalidID said:
$$y+siny=x$$

How would you even graph a function like this if you can't solve for y explicitly?
Graph y= x+ sin(x), then flip the x and y axes.
 

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