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Let A=[1sin⁡θ1−sin⁡θ1sin⁡θ−1−sin⁡θ1]A=\begin{bmatrix}1 & \sin\theta & 1\\-\sin\theta & 1 & \sin\theta\\-1 & -\sin\theta & 1\end{bmatrix}, where θ∈[0,2π]\theta\in[0,2\pi] then which of the following statements are correct?

A. ∣A∣=2+2sin⁡2θ|A|=2+2\sin^2\theta

B. Maximum value of ∣A∣|A| is 1.

C. Maximum value of ∣A∣|A| is –1.

D. ∣A∣∈[2,4]|A|\in[2,4]

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

Expanding along the first row: ∣A∣=(1+sin⁡2θ)−sin⁡θ(0)+(sin⁡2θ+1)=2+2sin⁡2θ|A|=(1+\sin^2\theta)-\sin\theta(0)+(\sin^2\theta+1)=2+2\sin^2\theta. As sin⁡2θ\sin^2\theta varies over [0,1][0,1], ∣A∣|A| varies over [2,4][2,4], so the maximum is 4. Hence A and D are correct.

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