matrix question

[Radical Edward]

can anyone think of a clever way to find the determinant of the following matrix, preferably by row reduction and laplace development:

 

|cos:lctheta: 1 0|

| 1 2cos:lctheta: 1|

| 0 1 2cos:lctheta:|

 

I know the answer, that isn't the problem, but I hate multiplying out entire matrices.

[Dave]

ick, matrices.

 

I can't do these (because I've never looked at them) but I'll see what I can find out for you.

[Radical Edward]

thanks, the answer is cos3:lctheta: by the way. I can do it by just finding the determinant and using trig identities, but I just wondered if there was a clever way