trig
posted by Lisa on .
evaluate the trigonometry function using its period as an aid cos(7pi/3)

7/3 = 2 1/3
2 pi is a full circle
so we have gone around clockwise two circles and pi/3
so we really want cos (pi/3)
draw a picture of that,60 degrees below the x axis in quadrant 4
the cosine is cos 60 degrees which is 1/2