If \(\theta \in\left(0, \frac{\pi}{2}\right)\), then \(\left|\begin{array}{ccc} (\sin…

If \(\theta \in\left(0, \frac{\pi}{2}\right)\), then \(\left|\begin{array}{ccc} (\sin \theta+\operatorname{cosec} \theta)^2 & (\sin \theta-\operatorname{cosec} \theta)^2 & 2020 \\ (\cos \theta+\sec \theta)^2 & (\cos \theta-\sec \theta)^2 & 2020 \\ (\tan \theta+\cot \theta)^2 & (\tan \theta-\cot \theta)^2 & 2020 \end{array}\right|=\)
  1. 1
  2. -1
  3. 0
  4. 2020

Solution

Given determinate, where \(\theta \in\left(0, \frac{\pi}{2}\right)\) is \(\Delta=\left|\begin{array}{ccc} (\sin \theta+\operatorname{cosec} \theta)^2 & (\sin \theta-\operatorname{cosec} \theta)^2 & 2020 \\ (\cos \theta+\sec \theta)^2 & (\cos \theta-\sec \theta)^2 & 2020 \\ (\tan \theta+\cot \theta)^2 & (\tan \theta-\cot \theta)^2 & 2020 \end{array}\right|\) On applying \(C_1 \rightarrow C_1-C_2\), we get \(\Delta=\left|\begin{array}{ccc} 4 & (\sin \theta-\operatorname{cosec} \theta)^2 & 2020 \\ 4 & (\cos \theta-\sec \theta)^2 & 2020 \\ 4 & (\tan \theta-\cot \theta)^2 & 2020 \end{array}\right|\) \(\because\) Elements of columns \(C_1\) and \(C_2\) are perportional, so \(\Delta=0\) Hence, option (c) is correct.

Asked in: AP EAMCET 2020 (21 Sep Shift 1)

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