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.

Printable View

- Feb 25th 2009, 02:17 PMmathg33khelp...
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. - Feb 25th 2009, 04:04 PMskeeter
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

since , there are no other real solutions for

... told you it wasn't "nice". - Feb 25th 2009, 04:18 PMmathg33k
ok thanks that helps a lot.

- Feb 27th 2009, 11:19 PMekledes
notice

if cos (x)=1 this means x=0,360,2*360,..... - Feb 28th 2009, 06:59 AMskeeter