So you obviously know that you have to plot the tangent functions graph using your unit circles and a table of values. Once you are done with that, you need to establish improvements/refinements to your method of getting precise measurements to craft a function that does a good job of modeling the "simple harmonic motion" of a mass suspended at the end of a spring. Think about:

(a) Number of oscillations in a given time period.
(b) The period (time taken for one oscillation).
(c) The lowest height, the greatest height and the equilibrium position.
(d) How you can utilize all the members of your group in an efficient way.
There may be other considerations and you should certainly discuss them using the blog. On Friday, without a single minute to waste, you must be ready to commence with your function modeling exercise. The end goal is that you come up with a function that fairly accurately models the motion of the suspended mass.