Question

please, please help?
find all solutions of the given equation in the interval [0,2pi)
cos3x=-cos3x

Answer 1

x=0, pi/6

Answer 2

@vipergirl81
ANSWER CHOICES:

Answer 3

You have cos(3x) = -cos(3x). Theres only one number that is equal to its own negative, and thats 0. Therefore:
cos(3x)=0
Since, if cos(3x) is equal to any other number, the original won't be true. This is because you can't have a number be equal to the negative of itself, unless that number is zero.
Now, just solve the following equation within your domain:
\[\cos(3x)=0\]Where does cosine equal 0?

Answer 4

@vinnv226 i got pi/6, pi/2, 5pi/6.... is that right?

Answer 5

Yes, thats what I got as well. You could check it by using a unit circle or graphing the equation

Answer 6

thanks!