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Without Expanding, Show that the Value of the Following Determinant is Zero: ∣ ∣ ∣ ∣ ∣ Sin α Cos α Cos ( α + δ ) Sin β Cos β Cos ( β + δ ) Sin γ Cos γ Cos ( γ + δ ) ∣ ∣ ∣ ∣ ∣

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प्रश्न

Without expanding, show that the value of the following determinant is zero:

\[\begin{vmatrix}\sin\alpha & \cos\alpha & \cos(\alpha + \delta) \\ \sin\beta & \cos\beta & \cos(\beta + \delta) \\ \sin\gamma & \cos\gamma & \cos(\gamma + \delta)\end{vmatrix}\]

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उत्तर

\[\begin{vmatrix}\sin\alpha & \cos\alpha & \cos(\alpha + \delta) \\ \sin\beta & \cos\beta & \cos(\beta + \delta) \\ \sin\gamma & \cos\gamma & \cos(\gamma + \delta)\end{vmatrix}\]
\[ = \begin{vmatrix}\sin\alpha\sin\delta & \cos\alpha\cos\delta & \cos(\alpha + \delta) \\ \sin\beta\sin\delta & \cos\beta\cos\delta & \cos(\beta + \delta) \\ \sin\gamma\sin\delta & \cos\gamma\cos\delta & \cos(\gamma + \delta)\end{vmatrix} \left[\text{ Applying }C_1 \to \sin\delta C_1 \text{ and }C_2 \to \cos\delta C_2 \right]\]
\[ = \begin{vmatrix}\sin\alpha\sin\delta & \cos(\alpha + \delta) & \cos(\alpha + \delta) \\ \sin\beta\sin\delta & \cos(\beta + \delta) & \cos(\beta + \delta) \\ \sin\gamma\sin\delta & \cos(\gamma + \delta) & \cos(\gamma + \delta)\end{vmatrix} \left[ \text{ Applying }C_2 \to C_2 - C_1 \right]\]
\[ = 0\]

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अध्याय 5: Determinants - Exercise 6.2 [पृष्ठ ५७]

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आर.डी. शर्मा Mathematics Volume 1 and 2 [English] Class 12
अध्याय 5 Determinants
Exercise 6.2 | Q 2.13 | पृष्ठ ५७

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