Some number belongs to real such that

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AI Thread Summary
The discussion revolves around the equation sin(x) = x - 1, where the user attempts to prove the existence of a real number x that satisfies this equation. They analyze the intervals for sin(x) and x - 1, concluding that there must be a real x between -1 and 1. However, a participant points out that while the proof of existence is correct, finding the specific value of x is more complex. The conversation highlights the importance of graphical representation in understanding the relationship between the two functions. Ultimately, the existence of such an x is confirmed, but its exact value remains elusive.
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Homework Statement



sin(x) = x - 1

Homework Equations





The Attempt at a Solution



i used the fact that -1 < sin(x) < 1
and set interval to [0, 2pi].

this gave me,

-1 < sin(x) < 1 and -1 < x - 1 < 2pi - 1
so therefore, since sin(x) < 1 < 2pi - 1
there must be x, real number that lies between -1 and 1.


is this correct?
 
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Draw a graph of y=sin(x) versus y=x-1.
 
You are correct in proving that such a x exists. Do you also need to find that x? That seems a bit difficult...
 
There is no such x between -1 and 1. That is not to say that such an x does not exist.
 
I tried to combine those 2 formulas but it didn't work. I tried using another case where there are 2 red balls and 2 blue balls only so when combining the formula I got ##\frac{(4-1)!}{2!2!}=\frac{3}{2}## which does not make sense. Is there any formula to calculate cyclic permutation of identical objects or I have to do it by listing all the possibilities? Thanks
Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks
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