Need help solving trig equations: 2 cos^2(x) = cos(x), etc

[Guest]

I'm not sure what type of questions these fall into, but I am stuck on them, and our sub in math is not much help. I'm turning to you guys to offer some assistance. Any help from you guys would be greatly appreciated.

--- Given 2 cos*x= cosx, solve for x in 0 <* x < 360

---- Given (2sin*x-3=4sinx) solve for x 0 <* x < 360

Note:

1.) * = squared
2.) <*= equal to OR less than

Another question I'm stuck on is ...

--- If secx= 17/8 with angle x in quadrant 4, find 2x.

 

[tkhunny]

Have you tried factoring?

2*cos²(x) = cos(x)
2*cos²(x) - cos(x) = 0
(2*cos(x) - 1)*cos(x) = 0

Now what?