# Solve give me some help

1. Feb 27, 2005

### aisha

Solve plz give me some help

how would you solve this question cos2x+cosx+1=0? The cos2x is throwing me off is that the same as cos^2x? Its multiple choice and all the answers are in radian how come?

Last edited: Feb 27, 2005
2. Feb 27, 2005

### AKG

1. cos(a + b) = cos(a)cos(b) - sin(a)sin(b).
2. Do you know how to write 1 in terms of sin and cos?

3. Feb 27, 2005

### aisha

no i dont plz help me

4. Feb 27, 2005

### Jameson

$$\sin^{2}x + \cos^{2}x = 1$$

5. Feb 27, 2005

### blue_soda025

cos2x is not the same as cos^2x. Use a double angle identity for that one.

6. Feb 28, 2005

### dextercioby

On normal basis,u should end up with a simple quadratic equation is "\cos x"...That won't be 2 hard to solve...

Daniel.