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থিম নির্বাচন

আপনার পছন্দের থিম বেছে নিন।

If  2cos^2theta-sintheta=1  then the value of  theta  is -- 

A.

π/6and(5π)/6

B.

(3π)/2

C. Both a and b
D. None of these 
সঠিক উত্তরঃ C. Both a and b
Explanation:

Another Explanation (5): ```html Given, \(2\cos^2\theta - \sin\theta = 1\) We know, \(\cos^2\theta = 1 - \sin^2\theta\) So, \(2(1 - \sin^2\theta) - \sin\theta = 1\) \(2 - 2\sin^2\theta - \sin\theta = 1\) \(2\sin^2\theta + \sin\theta - 1 = 0\) Let \(x = \sin\theta\) \(2x^2 + x - 1 = 0\) \(2x^2 + 2x - x - 1 = 0\) \(2x(x+1) - 1(x+1) = 0\) \((2x - 1)(x+1) = 0\) So, \(2x-1=0\) or \(x+1=0\) \(x = \frac{1}{2}\) or \(x = -1\) Case 1: \(\sin\theta = \frac{1}{2}\) \(\theta = \sin^{-1}(\frac{1}{2})\) \(\theta = 30^\circ, 150^\circ\) 🥳🎉 Case 2: \(\sin\theta = -1\) \(\theta = \sin^{-1}(-1)\) \(\theta = 270^\circ\) ✨🎈 Therefore, the values of \(\theta\) are \(30^\circ\), \(150^\circ\), and \(270^\circ\). 😊👍 The answer "Both a and b" implies that there are two options, 'a' and 'b', which are both correct. Without knowing the specific options 'a' and 'b', we cannot definitively say which angles they represent. However, based on our calculation, possible options could be related to \(30^\circ\), \(150^\circ\), or \(270^\circ\). 🧐🤔 ```