Mathematics

Mathematics

Problem

If AA, BB, CC be the angles of a triangle, then ∣−1cos⁡Ccos⁡Bcos⁡C−1cos⁡Acos⁡Bcos⁡A−1∣=\begin{vmatrix} -1 & \cos C & \cos B \\ \cos C & -1 & \cos A \\ \cos B & \cos A & -1 \end{vmatrix} = (a) 1 (b) 0 (c) cos⁡Acos⁡Bcos⁡C\cos A \cos B \cos C (d) cos⁡A+cos⁡Bcos⁡C\cos A + \cos B \cos C (a) 1 (b) 0 (c) cos⁡Acos⁡Bcos⁡C\cos A \cos B \cos C (d) cos⁡A+cos⁡Bcos⁡C\cos A + \cos B \cos C

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