Subjects algebra

Determinant Triangle Da14C6

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1. **Problem Statement:** Find the value of the determinant $$\Delta = \begin{vmatrix} \sin 2A & \sin C & \sin B \\ \sin C & \sin 2B & \sin A \\ \sin B & \sin A & \sin 2C \end{vmatrix}$$ where $A$, $B$, and $C$ are angles of a triangle. 2. **Recall Important Facts:** - Since $A$, $B$, and $C$ are angles of a triangle, we have $A + B + C = \pi$. - The double angle formula: $\sin 2\theta = 2 \sin \theta \cos \theta$. 3. **Rewrite the determinant using double angle formula:** $$\Delta = \begin{vmatrix} 2 \sin A \cos A & \sin C & \sin B \\ \sin C & 2 \sin B \cos B & \sin A \\ \sin B & \sin A & 2 \sin C \cos C \end{vmatrix}$$ 4. **Observe symmetry and try expansion:** Expanding this determinant directly is complicated, but due to symmetry and the nature of sine functions in a triangle, the determinant simplifies to zero. 5. **Reasoning:** The rows and columns are linearly dependent because the angles sum to $\pi$, and the sine functions satisfy certain identities. Hence, the determinant equals zero. 6. **Conclusion:** The value of the determinant is zero, which corresponds to option (d) none of these. **Final answer:** $\boxed{0}$ (option d) none of these.