1. The problem statement, all variables and given/known data That is prove that |a•c|≤|a||c| for any vector a=<a1,a2,a3> & c=<c1,c2,c3> 2. Relevant equations 3. The attempt at a solution I really dont have much of an attempt at the solution. Im not sure where to start. I can kind of justify it in my mind by saying the sum of two magnitudes will always be a positive number and if 1 of the the a1 c1 etc where negative it could bring the value down but that is no where near a proof. Where does one even begin to start justifying this?