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Consider the following statements: I...

Consider the following statements:
I. `n(sin^2 67(1^@)/(2)-sin^2 22 (1^@)/(2)) gt 1` for all positive integers `n ge 2`.
II. If x is any positive real number, then `nx gt 1` for all positive integers `n ge 2`.
Which of the above statements is/are correct?

A

A) Only I

B

B) Only II

C

C) Both I and II

D

D) Neither I nor II

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question, we need to analyze the two statements provided and determine their validity. **Statement I:** We need to verify if \( n(\sin^2(67.5^\circ) - \sin^2(22.5^\circ)) > 1 \) for all positive integers \( n \geq 2 \). 1. **Calculate \( \sin^2(67.5^\circ) \) and \( \sin^2(22.5^\circ) \)**: - We can use the identity \( \sin^2(x) = \frac{1 - \cos(2x)}{2} \). - For \( \sin^2(67.5^\circ) \): \[ \sin^2(67.5^\circ) = \frac{1 - \cos(135^\circ)}{2} = \frac{1 - (-\frac{1}{\sqrt{2}})}{2} = \frac{1 + \frac{1}{\sqrt{2}}}{2} = \frac{2 + \sqrt{2}}{4} \] - For \( \sin^2(22.5^\circ) \): \[ \sin^2(22.5^\circ) = \frac{1 - \cos(45^\circ)}{2} = \frac{1 - \frac{1}{\sqrt{2}}}{2} = \frac{2 - \sqrt{2}}{4} \] 2. **Subtract the two values**: \[ \sin^2(67.5^\circ) - \sin^2(22.5^\circ) = \frac{2 + \sqrt{2}}{4} - \frac{2 - \sqrt{2}}{4} = \frac{(2 + \sqrt{2}) - (2 - \sqrt{2})}{4} = \frac{2\sqrt{2}}{4} = \frac{\sqrt{2}}{2} \] 3. **Multiply by \( n \)**: \[ n(\sin^2(67.5^\circ) - \sin^2(22.5^\circ)) = n \cdot \frac{\sqrt{2}}{2} \] 4. **Check if \( n \cdot \frac{\sqrt{2}}{2} > 1 \)** for \( n \geq 2 \): - For \( n = 2 \): \[ 2 \cdot \frac{\sqrt{2}}{2} = \sqrt{2} \approx 1.414 > 1 \] - For \( n = 3 \): \[ 3 \cdot \frac{\sqrt{2}}{2} = \frac{3\sqrt{2}}{2} \approx 2.121 > 1 \] - This holds true for all \( n \geq 2 \). **Conclusion for Statement I**: True. --- **Statement II:** We need to verify if \( nx > 1 \) for all positive integers \( n \geq 2 \) and any positive real number \( x \). 1. **Choose a counterexample**: - Let \( n = 2 \) and \( x = \frac{1}{4} \): \[ nx = 2 \cdot \frac{1}{4} = \frac{1}{2} < 1 \] **Conclusion for Statement II**: False. --- **Final Conclusion**: - Statement I is correct. - Statement II is incorrect. Thus, the correct answer is that only Statement I is true.
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