So with the help from the last question I am finalizing things before finals next week and I am trying to rework this question over and over to see how I can improve my grade on it/where I screwed up. I am attaching a picture of it because of the graph.

I received 6/10 points on this assignment. Here was my work.

with p(t) given and I need to evaluate it at 1000 hares. I just set the equation equal to 1,000 with gave me

1000=1500*cos(pi/60(t-30))+2000. and all of this reduced down to the following in the end

-1000/1500=cos(pi/60(t-30)) followed by

cos^-1(-1000/1500) but clearly I am missing something here as I only received 6/10 and I kinda think that was pitty points >.<

Or should I have done something as simple as following the 1,000 line i drew across the graph and just found where it intersected and get my population from that.