1. The problem statement, all variables and given/known data find the inverse laplace transform. 1/(s^3 + 7s) 2. Relevant equations sin(kt) = k/(s^2 + k^2) cos(kt) = s/(s^2 + k^2) 3. The attempt at a solution so this one is different from all the others I have done because it involves an imaginary number and I am not sure what the rule is that changes the problem. somehow the answer becomes 1/7 - cos(sqrt(7)*t ) / 7 but I am getting positive sine instead of negative cosine and 7i in the denominator instead of 7. does the i reverse sine to cosine or something?