1. The problem statement, all variables and given/known data The displacement of a mass as a function is given by the equation x = 3cos((10pi )t) + 3cos((11\pi)\t) What is the time between beats, i.e the time between occurrence of the maximum displacement? 2. Relevant equations At a maximum v = 0 3. The attempt at a solution I took the derivative of the function and set it equal to zero 10sin((10pi)t) + 11sin((11pi)t) = 0 I can't find an analytical way of solving this problem. I have tried various trig identities , expanding the functions which took an hour but go no where. Is my strategy of finding the zeros this way the right one or should I come up with a different strategy. And if the latter than where should I start from?