Question

which of the following best explains why cos 2pi/3 is not equal to cos 5pi/3
A.The angles do not have the same reference angle.
B.Cosine is negative in the second quadrant and positive in the fourth quadrant.
C.Cosine is positive in the second quadrant and negative in the fourth quadrant.
D.The angles do not have the same reference angle or the same sign.

Answer 1

B.)- Cosine is negative in the second quadrant and positive in the fourth quadrant. 

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Answer 2

In this exercise we have to use the knowledge of cosine quadrants, like this:

Letter B

We have that the quadrant of the cosine is given by:

• The two quadrants on the right are positive.
• The two quadrants on the left are negative.

So we know that:

$cos (2\pi/3)$ If it's in quadrant three, that's negative.

$cos(5\pi/3)$ If you're in quadrant four, that's positive.

See more about cosine at brainly.com/question/14290164