The sound wave of two music notes can be represented by the function y = -2cos2x and y = cos2x, where x represents the time since the note is played. At what times will the frequencies of the sound waves be the same in the interval [0°, 360°)?

A. x = 0º, 180º, 270º, 300º

B. x = 60º, 120º, 240º, 300º

C. x = 0º, 60º, 120º, 180º

D. x = 60º, 100º, 140º, 180º

Question

The sound wave of two music notes can be represented by the function y = -2cos2x and y = cos2x, where x represents the time since the note is played. At what times will the frequencies of the sound waves be the same in the interval [0°, 360°)?

A. x = 0º, 180º, 270º, 300º

B. x = 60º, 120º, 240º, 300º

C. x = 0º, 60º, 120º, 180º

D. x = 60º, 100º, 140º, 180º

Maya12 · Answer

@oliver69 you always need oliver.

Aiden3j · Answer

I think its B im not sure though i need @oliver69 to double check for me

OLIVER69 · Answer

I am not too bright with this but I did some research and I do believe it is D... @narad can you check

Narad · Answer

Both waves have the same period T
$$T=180º$$
Frequency is 
$$f=\frac{ 1 }{ T }$$
I may believe that it is answer A

kekeman · Answer

Lol wow okay three different answers, but thanks!

kekeman · Answer

So its "x = 0º, 180º, 270º, 300º"

kekeman · Answer

@narad wrote:

Both waves have the same period T $$T=180º$$ Frequency is $$f=\frac{ 1 }{ T }$$ I may believe that it is answer A

????