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Find the Maximum Value of ∣ ∣ ∣ ∣ 1 1 1 1 1 + Sin θ 1 1 1 1 + Cos θ ∣ ∣ ∣ ∣ - Mathematics

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Question

Find the maximum value of \[\begin{vmatrix}1 & 1 & 1 \\ 1 & 1 + \sin \theta & 1 \\ 1 & 1 & 1 + \cos \theta\end{vmatrix}\]

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Solution

Let Δ = \[\begin{vmatrix}1 & 1 & 1 \\ 1 & 1 + \sin \theta & 1 \\ 1 & 1 & 1 + \cos \theta\end{vmatrix}\]

Applying

\[R_2 \to R_2 - R_1\] and 
\[R_3 \to R_3 - R_1\], we get
\[∆ = \begin{vmatrix}1 & 1 & 1 \\ 0 & \sin\theta & 0 \\ 0 & 0 & \cos\theta\end{vmatrix}\] 

\[= \sin\theta\cos\theta\]

\[ = \frac{\sin2\theta}{2}\]

We know that −1 ≤ sin2θ ≤ 1.
∴ Maximum value of ∆ = \[\frac{1}{2} \times 1 = \frac{1}{2}\]
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Chapter 6: Determinants - Exercise 6.6 [Page 95]

APPEARS IN

RD Sharma Mathematics [English] Class 12
Chapter 6 Determinants
Exercise 6.6 | Q 53 | Page 95

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