X=2π/3
find the exact value of cos(x). include a drawing of your reference triangle to receive full credit.

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Reference angle is

Step-by-step explanation:

Given the value of x. we have to find the correct value of cosx.

Now, we have to find the exact value of

Now, we have to find the reference angle of .

Since the angle lies in second quadrant, the reference angle formula is

Reference angle= .

                           =

the answer will be the last one