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Consider an equation z^(197)=1(z is a co...

Consider an equation `z^(197)=1`(`z` is a complex number). If `alpha, beta` are its two randomly chosen roots. `'p'` denotes the probability that `sqrt(2+sqrt(3)) le|alpha+beta|`, then

A

`p=1/1996,aepsilonI`

B

`[1/p]` lies in `[5,15]`

C

`[1/pxx83/50]` is 8 is divisible by 2

D

`[1/p]+2` is 6

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the equation \( z^{197} = 1 \) and find the probability \( p \) that \( \sqrt{2 + \sqrt{3}} \leq |\alpha + \beta| \) for two randomly chosen roots \( \alpha \) and \( \beta \). ### Step 1: Identify the roots of the equation The equation \( z^{197} = 1 \) has 197 distinct roots, which are the 197th roots of unity. These roots can be expressed as: \[ z_k = e^{2\pi i k / 197} \quad \text{for } k = 0, 1, 2, \ldots, 196 \] ### Step 2: Express \( \alpha + \beta \) Let \( \alpha = z_j = e^{2\pi i j / 197} \) and \( \beta = z_k = e^{2\pi i k / 197} \). Then: \[ \alpha + \beta = e^{2\pi i j / 197} + e^{2\pi i k / 197} \] Using the formula for the sum of two complex exponentials: \[ \alpha + \beta = 2 \cos\left(\frac{2\pi (j - k)}{2 \cdot 197}\right) \cdot e^{\frac{2\pi i (j+k)}{2 \cdot 197}} \] ### Step 3: Calculate the modulus The modulus of \( \alpha + \beta \) is given by: \[ |\alpha + \beta| = |2 \cos\left(\frac{\pi (j - k)}{197}\right)| \] We need to find the condition under which: \[ |\alpha + \beta| \geq \sqrt{2 + \sqrt{3}} \] ### Step 4: Simplify the inequality Squaring both sides gives: \[ 4 \cos^2\left(\frac{\pi (j - k)}{197}\right) \geq 2 + \sqrt{3} \] This simplifies to: \[ \cos^2\left(\frac{\pi (j - k)}{197}\right) \geq \frac{2 + \sqrt{3}}{4} \] ### Step 5: Find the angle corresponding to the cosine value Let \( c = \frac{2 + \sqrt{3}}{4} \). The cosine value can be calculated: \[ \cos\left(\theta\right) = \sqrt{c} \implies \theta = \cos^{-1}\left(\sqrt{c}\right) \] We need to find the angles \( \theta \) such that: \[ \frac{\pi (j - k)}{197} \in [-\theta, \theta] \] ### Step 6: Count the favorable outcomes The total number of pairs \( (j, k) \) is \( 197^2 \). The number of favorable pairs \( (j, k) \) where \( |\alpha + \beta| \geq \sqrt{2 + \sqrt{3}} \) can be calculated based on the range of \( j - k \) that satisfies the cosine condition. ### Step 7: Calculate the probability Let \( N \) be the number of favorable pairs. The probability \( p \) is given by: \[ p = \frac{N}{197^2} \] ### Step 8: Final computation From the video transcript, we find that \( N = 332 \), thus: \[ p = \frac{332}{197^2} = \frac{332}{1996} \] ### Conclusion The final answer for the probability \( p \) is: \[ p = \frac{332}{1996} \]

To solve the problem, we need to analyze the equation \( z^{197} = 1 \) and find the probability \( p \) that \( \sqrt{2 + \sqrt{3}} \leq |\alpha + \beta| \) for two randomly chosen roots \( \alpha \) and \( \beta \). ### Step 1: Identify the roots of the equation The equation \( z^{197} = 1 \) has 197 distinct roots, which are the 197th roots of unity. These roots can be expressed as: \[ z_k = e^{2\pi i k / 197} \quad \text{for } k = 0, 1, 2, \ldots, 196 \] ...
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