Let x be a solution to the equation x 2 + x + 2 0 1 4 = 0 .
Find the value of n → ∞ lim n i = 1 ∏ 2 n ∣ ∣ ∣ ∣ 2 0 1 4 2 i − 1 x i + 1 ∣ ∣ ∣ ∣ .
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Yes, I also think that 2 0 1 3 is wrong. I got 2 0 1 4 as follows:
Note that x = 2 − 1 + 3 i 8 9 5 = 2 0 1 4 c i s ( π − arctan ( 3 8 9 5 ) )
Now, let's change i for k to avoid confusions. I got this after some algebra:
∣ ∣ ∣ ∣ 2 0 1 4 2 k − 1 x k + 1 ∣ ∣ ∣ ∣ = 2 0 1 5 + 2 2 0 1 4 cos ( k ( π − arctan ( 3 8 9 5 ) ) )
So, we are looking for:
lim n → ∞ ∏ k = 1 2 n 2 n 2 0 1 5 + 2 2 0 1 4 cos ( k ( π − arctan ( 3 8 9 5 ) ) )
Honestly I don't know how to solve that limit, but after some iterations I noticed that it converges to 2 0 1 4 . Any thoughts?
I think Power of a Point cannot be applied to the center of the circle but could be applied to the origin and give the right answer 2013
....the answer is 2013.
The only problem in the solution is that point X should be the origin, not 1 .
As i varies form 1 to 2n and limit n tends to infinity that is n belongs to natural number so their are discontinuous point on circle s I am not clear about the condition that X,P, Q are collinear if n belongs to R then answer will be 2013 but if n belongs to N then limiting value tens to 2014.
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By definition, n is a natural number.
Is that so? That's pretty interesting. So is the answer 2 0 1 4 after all?
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First, note that both solutions of x 2 + x + 2 0 1 4 = 0 have a magnitude of 2 0 1 4 and a irrational argument. This means that as n → ∞ , the values of 2 0 1 4 2 i − 1 x i + 1 where 1 ≤ i ≤ n become the set of points with distance 2 0 1 4 away from 1 on the complex plane (because ∣ ∣ ∣ ∣ 2 0 1 4 2 i − 1 x i ∣ ∣ ∣ ∣ = 2 0 1 4
Thus, ∣ ∣ ∣ ∣ 2 0 1 4 2 i − 1 x i + 1 ∣ ∣ ∣ ∣ are the distances between the circle of radius 2 0 1 4 and center 1 and the origin.
Also, n i = 1 ∏ 2 n stuff = 2 n i = 1 ∏ n stuff = n i = 1 ∏ n stuff 2
Thus we just need to find the square of the geometric mean of all the distances between the origin and the circle.
Now given any point P on the circle, draw a line through that point and 1 . The line will cross the circle at another point Q . If we let 1 be point X , then by Power of a Point, ( P X ) ( Q X ) = ( 2 0 1 4 + 1 ) ( 2 0 1 4 − 1 ) = 2 0 1 3 .
However, we can apply this strategy for any point P on the circle, and since the geometric mean of any two opposite distances on the circle (the P X and the Q X ) is always ( P X ) ( Q X ) = 2 0 1 3 , then the geometric mean of the entire thing is also 2 0 1 3 .
However, we wanted the square of the geometric mean, so our answer is 2 0 1 3 2 = 2 0 1 3 .
I have a feeling in my gut that this answer is wrong and we need calculus.