Question 306787
Draw the unit circle.


2pi/3 radians is equivalent to 120 degrees.


This means that your terminal arm will create an angle of 60 degrees with the x axis, in the second quadrant.


Secant = 1/Cosine


The value of Cos(120) can then be found from the 30-60-90 triangle drawn in the second quadrant, as 120 degrees has a reference angle of 60 degrees. (This would probably make more sense with a picture, but I don't know how to draw one on here.)


Cos(120)=-1/2


Sec(120) = -2/1 = -2


Let me know if you need any clarifications.