Sinx -x/2= 0

  • Thread starter sporus
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  • #1
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Homework Statement



sinx -x/2= 0

Homework Equations





The Attempt at a Solution



i don't even know where to start
 

Answers and Replies

  • #2
Mentallic
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Well if it asked you just, [tex]\sin(\theta)=0[/tex] what would be your answer for [itex]\theta[/itex]?
 
  • #3
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i know that the answer is zero, but i might not get full marks if i don't do it algebraically
 
  • #4
Mentallic
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The answer isn't just 0. What about [itex]\pi[/itex]? In fact there are an infinite number of solutions. Did the question say anywhere to find the solutions to this problem for some restricted value of x, say [tex]0\leq x\leq 2\pi[/tex]?
 
  • #5
vela
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Are you trying to find all x for which sin x = x/2? You can't solve that algebraically.
 
  • #6
Mentallic
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Oh I completely missed the sinx-x/2=0, sorry, I read it as sin(-x/2)=0...

Yes as vela said, you can't solve it algebraically, you'll have to solve it numerically.
 
  • #7
ehild
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Plot sin(x)-x/2 (do not forget that x is in radians) and find the approximate x values where it is zero.
Then pick up one of these and try the iteration

xk+1=2 sin(xk).


ehild
 
  • #8
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thanks. plotting sinx - x/2 is a bit hard so i plotted sinx and x/2 and found the intersection point.
 

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