1.

The value of the determinant `|(cos alpha, -sin alpha,1),(sin alpha,cos alpha,1),(cos(alpha+beta),-sin(alpha+beta),1)|` is equalA. independent of `alpha`B. independent of `beta`C. independent of `alpha and beta`D. none of these

Answer» Correct Answer - A
We have, `|(cos alpha,- sin alpha,1),(sin alpha,cos alpha,1),(cos (alpha + beta),- sin (alpha + beta),1)|`
`= |(cos alpha,- sin alpha,1),(sin alpha,cos alpha,1),(0,0,1 + sin beta - cos beta)| " " ["Applying "R_(3) rarr R_(3) - R_(1) (cos beta) + R_(2) (sin beta)]`
`= (1 + sin beta - cos beta) (cos^(2) alpha + sin^(2) alpha)`
`= 1 + sin beta - cos beta`, which is independent of `alpha`


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