I really need helpo with this question. I am having to revise over easter for the three week break and i need a solution to this. I have all the past exam papers but the lecturere doesnt have any past paper solutions and his lecture notes are vague. TO top it off i wondered if there were any good books with worked examples and questions? Here is my problem. At time t, the position vector of a point P, on a fairground ride is given by: r(t) = (2cost + cos4t)i + (2sint + sin4t)j m Find its acceleration, F, at time t. Show that: |f|^2 = 260 + 64 cos3t m^2s^-4 Ok thats the problem. Now i have managed to get the velocity by differentiation and then the acceleration which works out to be: a(t) = (-2cost-16cos4t)i + (-2sint-16sin4t)j But i cant then get this expression to work out to |f|^2 = 260 + 64 cos3t... Can anyone help?