Question

Please help!!
find all solutions of the following equation in the interval [0,2π)

cos3x=-cos3x

Answer 1

are you sure that you copied the question down correctly?

Answer 2

oh theres a negative on the right side

Answer 3

let m = 3x
\[\cos(m) = -\cos(m)\]
\[\cos(m) + \cos(m) = 0\]
\[2\cos(m) = 0\]
\[\cos(m) = 0\]
\[m = \pi/2 * k \pi\]
where k is an element of the integers
\[3x = \pi/2 * k \pi\]
\[x = \pi/6 * k \pi/3\]

Answer 4

@alexandercpark i got that i just didnt know what the answer was... here are the choices: