1.

If `Delta = |(cos (alpha_(1) - beta_(1)),cos (alpha_(1) - beta_(2)),cos (alpha_(1) - beta_(3))),(cos (alpha_(2) - beta_(1)),cos (alpha_(2) - beta_(2)),cos (alpha_(2) - beta_(3))),(cos (alpha_(3) - beta_(1)),cos (alpha_(3) - beta_(2)),cos (alpha_(3) - beta_(3)))|" then " Delta` equalsA. `cos alpha_(1) cos alpha_(2) cos alpha_(3) cos beta_(1) cos beta_(2) cos beta_(3)`B. `cos alpha_(1) + cos alpha_(2) + cos alpha_(3) + cos beta_(1) + cos beta_(2) + cos beta_(3)`C. `cos (alpha_(1) - beta_(1)) cos (alpha_(2) - beta_(2)) cos (alpha_(3) - beta_(3))`D. none of these

Answer» Correct Answer - D
We have, `Delta = |("cos" alpha_(1),"sin" alpha_(1),0),("cos" alpha_(2),"sin" alpha_(2),0),("cos" alpha_(3),"sin" alpha_(3),0)||("cos" beta_(1),"sin "beta_(1),0),("cos" beta_(2),"sin" beta_(2),0),("cos"beta_(3),"sin "beta_(3),0)|`
`rArr Delta = 0 xx 0 = 0`


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