Question

Solve each equation for x if 0 ≤ x < 2pi. give answers in radian values only

Cos2x-cosx-2=0

Answer 1

is the 2 ^2?

Answer 2

Can you solve this? \(y^{2} - y - 2 = 0\)

Answer 3

Its not ^2

Answer 4

I'm assuming you mean \(\cos^{2}(x)\) and not \(\cos(2x)\).

Answer 5

No in the textbook its Cos 2x.

Answer 6

Fair enough. \(\cos(2x) = 2\cos^{2}(x) - 1 \)

Thus,

\(\cos(2x) - \cos(x) - 2 = 2\cos^{2}(x) - 1 - \cos(x) - 2 = 2\cos^{2}(x) - \cos(x) - 3 = 0\)

This changes my question to...

Can you solve this? \(2y^{2} - y - 3 = 0\)

Answer 7

I forgot how to factor lol.

Answer 8

x^2+5x+6x
(x+3)(x+2)

Answer 9

ahh Yes
I recall this.

Answer 10

what now?

Answer 11

what did you get when you factored?