1. The problem statement, all variables and given/known data L[cos(at)cosh(at)] = ? 2. Relevant equations L[cos(at)] = s/(s^2 + w^2) 3. The attempt at a solution I'm able to get the solution given that is (s^3)/(s^4 + 4a^4) The question requested to use first shift property. So I used cosh(at) = 1/2[e^at + e^(-at)] but now I'm trying to use another method. if you use euler's rule, you can also get cos(at) = cosh(at) = 1/2[e^at + e^(-at)] then simply multiply them and get L[e^2at + 2 + e^(-2at)] but I dont seem to get the same solution as above, any ideas?