<PRE><B>Question 22230</B>
  s =4sin(t+30), and a force acting upon the body is given by F=7sin(t-60).  If the energy of the motion, E, at at time t is the product Fs, show that 
E=-14cos(2t-30)


Use the formula:

 2 sin A sin B = cos (A-B) - cos(A+B) and cos 90 deg= 0

 Kenny
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