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Ask iit jee aieee pet cbse icse state board community Community Discussion Question: Find the number of solutions.
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pantpranav (387)

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Find the number of solutions of the equation:


x / 100 = sin x .

    
umang_cool (2)

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the solution 0.


sin 0 = 0


therefore  lhs=rhs


and no other value will satisfy the eqution

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umang_cool (2)

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the solution 0.


sin 0 = 0


therefore  lhs=rhs


and no other value will satisfy the eqution.


therefore no. of solutions is 1

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jishnudas1991 (1020)

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There are more than one solutions.


let me find out how many..............


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jishnudas1991 (1020)

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Re:Find the number of solutions.


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pantpranav (387)

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Good attempt.
But the answer is 63.



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jishnudas1991 (1020)

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The number of solutions won't change even if we rewrite the equation as:


sin[10x]=x/10


here's the graph of this function


this verifies that the answer I derived mathenatically was not correct.


63 is correct but where have I gone wrong!!! 



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jishnudas1991 (1020)

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I found the number of complete loops(15)


but as you can see the 16 th loop also gave two solutions which i did not take into account


so the total no of solutions for x>0 are 31


x<0 are also 31


and x=0 is also a solution


total:63 solutions.


 


 


 Not that this sum could not be done without the aid of a computer generated graph.


we could have found the number of halfloops of sin[x] for x<100  (n=[100/pi] =31;[ ]=gif])


then.Now see that the number of halfloops in which sinx is positive is16


so there are 16*2=32 solutions for x>=0.similarly since sinx-(x/100) is odd more 31 solutions exist for x<0total 63 solutions.but even hand drawn graphs will be helpful in this case.............


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sahilgupta_iit (612)

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Solve using graphs of the two functions; y=x/100 and y=sinx
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