Practicing Success
Let $Δ=\begin{vmatrix} 1 & sin \theta & 1\\-sin\theta & 1 & sin \theta \\-1 & -sin \theta & 1 \end{vmatrix}$ then Δ lies in the interval : |
[2, 3] [2, 4] [3, 4] [4, 2] |
[2, 4] |
The correct answer is Option (2) → [2, 4] $Δ=\begin{vmatrix} 1 & sin \theta & 1\\-sin\theta & 1 & sin \theta \\-1 & -sin \theta & 1 \end{vmatrix}$ $=1(1+\sin θ)+\sin θ(-\sin θ+\sin θ)+1(1+\sin^2 θ)$ $=2+2\sin^2 θ$ as $0≤\sin^2 θ≤1⇒1≤1+\sin^2 θ≤2$ so $2≤2(1+\sin^2 θ)≤4$ so $Δ∈[2, 4]$ |