Originally Posted by

**mathg33k** ok so i got this problem and i did a bunch of things to try and solve it and i just cant seem to get it....

Cos(X)*Cos(2x)=1

your help would be appreciated. thanks.

well, it's not very easy to be done by hand ...

use the identity

one obvious solution (and there is no other way to find it other than "observation") is

so, two solutions for x are or .

investigating other possible solutions ...

use synthetic division with the coefficients ...

Code:

1].........2..........0.........-1.........-1
.....................2...........2..........1
-----------------------------------------------
...........2..........2..........1..........0

the depressed polynomial is ...

since , there are no other real solutions for

... told you it wasn't "nice".