How to evaluate cos(2 pi/3)?

phasiwedi98z

phasiwedi98z

Answered question

2023-02-12

How to evaluate cos ( 2 π 3 )?

Answer & Explanation

Ryan Donovan

Ryan Donovan

Beginner2023-02-13Added 5 answers

If you are familiar with fundamental cosine values and radian angles, this should be simple.
π = 180 degrees
2 π = 180 2 degrees = 360 degrees
2 π 3 = 360 d e g r e e s 3 = 120 degrees
Knowing the unit circle allows you to recognize that cos ( 120 ) is the polar opposite of cos ( 60 ) (both in degrees). They are in distinct quadrants, which explains why.
Since cos ( 60 ) = 1 2
cos ( 120 ) = - 1 2

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