adding calculation to maclaurin series

• _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ the solution is___________________*

hello every one, I solved this problem in matlab based on the written solution I found the the absolute errors (Ea) based on the solution. how can I add calculating the true error (Ea) which is abs( true value - previous value/ true value) in other words how can I use matlab to change that previous value each step based on the true value 0.5 as the solution indicates in the zero order of this series abs(0.5-1/0.5). I want get the true error (et) after adding each term to my final answer until the indicated condition satisfies. this is what I did and it works for all except (et) I couldn't figure that out