1. The problem statement, all variables and given/known data So this is a really simple problem and i know I'm missing something really obvious but i just can't spot it. 2. Relevant equations 3. The attempt at a solution so in the second part above I get : e-x - ex/2i. However I don't get the next bit as the 2i on the denominator is now factored into the top equation to give -ie-x + iex/2. I don't get how the 2 equations are equivalent and what they've done to get the i from the denominator to the numerator. If anyone could explain how this happened that'd be great!