Ok so I am struggling with a question that I have been trying to figure out for a couple of days now. The professor told us the first part but i can't figure out the rest. Here is the question from the attached files:

According to our professor, question 1 becomes:

X(t) = 2[cos(7πt) + sqrt(9-sin2(7πt))]

Jest before someone asks, it is not graded HWK. It is an application problem which encompasses many of the things we have learnt in the last week. We get them every week and must try to get them (not necessary though).