Question

Find all solutions in the interval [0, 2π).

Answer 1

cos2x + 2 cos x + 1 = 0

Answer 2

Pleaseeeee Help me I don't understand!

Answer 3

Is the question
A. \(cos2x + 2 cos x + 1 = 0\)
or
B. \(cos^2x + 2 cos x + 1 = 0\)

Answer 4

The second one. (B)

Answer 5

general rule for quadratic form

Answer 6

(cos+1)^2=0

Answer 7

cosx=-1

Answer 8

ok so do I replace cosx with -1 in the equation?

Answer 9

@Catch.me means that the solution for cos(x) is cos(x)=-1.
Now you have to solve for x from the standard graph of cosine(x) between 0 and 2pi.

Here's what the graph looks like, from which you can interpret the value of x when cos(x)=-1.

Answer 10

So if cos x=-1
x =3pi/2?

Answer 11

Not really, but hope this will make it more clear.