JEE Mains · Maths · STD 11 - 8. sequence and series
For the functions \(f(\theta) = \alpha\tan^2\theta + \beta\cot^2\theta\), and \(g(\theta) = \alpha\sin^2\theta + \beta\cos^2\theta\), \(\alpha > \beta > 0\), let \(\min_{0 < \theta < \pi/2}f(\theta) = \max_{0 < \theta < \pi}g(\theta)\). If the first term of a G.P. is \(\left(\dfrac{\alpha}{2\beta}\right)\), its common ratio is \(\left(\dfrac{2\beta}{\alpha}\right)\) and the sum of its first \(10\) terms is \(\dfrac{m}{n}\), \(\gcd(m, n) = 1\), then \(m + n\) is equal to _______.
- A 1275
- B 1276
- C 1277
- D 1279
Answer & Solution
Correct Answer
(D) 1279
Step-by-step Solution
Detailed explanation
For the function \(f(\theta) = \alpha\tan^2\theta + \beta\cot^2\theta\), applying the AM-GM inequality gives: \(\alpha\tan^2\theta + \beta\cot^2\theta \ge 2\sqrt{\alpha\tan^2\theta \cdot \beta\cot^2\theta} = 2\sqrt{\alpha\beta}\) Thus, \(\min_{0 \beta > 0\), the maximum value of…
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