you can get the Period graphically if you see the points A and B are the upper points of the graph. if you subtract them you get the period
in this case, let me see
Here they give you the points where the graph cross the midline, if you see, that is half of the period, so
Period= 2* (5,1-(-1,7))= 13,6
You have to subtract the points to know the distance between that points, and the graph is
when you subtract the points, you are getting the distance between (for example) the green point on my draw
And the period is the time it takes for one complete oscillation, after this, it repeats over and over
So between 3 of these green points we have a period
to know the value, we need to know the distance between them (in this case (5,1-(-1,7))= 6,8
each square have 1 period on it, and the value is 2 times the distance between the green points
Answer:
Period= 2* (5,1-(-1,7))= 13,6