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If `alpha,beta and gamma` are such that `alpha+beta+gamma=0`, then `|(1,cos gamma,cosbeta),(cosgamma,1,cos alpha),(cosbeta,cos alpha,1)|`A. `cos alpha cos beta cos gamma`B. `cos alpha + cos beta + cos gamma`C. 1D. none of these

Answer» Correct Answer - D
Let A, B and C be three number such that `alpha = B -C, beta = C-A and gamma = A-B`. Clearly, `alpha + beta + gamma = 0`
`:. |(1,cos (A-B),cos (C-A)),(cos (A-B),1,cos (B-C)),(cos (C -A) ,cos (B -C),1)|`
`= |(cos^(2) A + sin^(2) A,cos A cos B + sin A sin B,cos A cos C + sin A sin C),(cos A cos B + sin A sin B,cos^(2) B + sin^(2) B,cos B cos C + sin B sin C),(cos C cos A + sin C sin A,cos B cos C + sin B sin C,cos^(2) C + sin^(2) C)|`
`= |(cos A ,sin A,0),(cos B,sin B,0),(cos C,sin C,0)||(cos A ,sin A,0),(cos B ,sin B,0),(cos C,sin C,0)| = 0 xx 0 = 0`


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