Why is the calculator saying there's an error when there shouldn't be?
The most frequent reason for this is because you are rounding the sides and angles which can, at times, lead to results that seem inaccurate. In these cases, in actuality , the calculator is really producing correct results. However, it is then rounding them for you- which leads to seemingly inaccurate results and possible error warnings. To see if that is your problem, set the rounding to maximum accuracy.