# WRONG SOLVED BUT CLOSED QUESTIONIt's about the proper solving of the problems!! I found a huge mistake in solving the following problem. The biggest problem was that I couldn't correct it, because...

It's about the proper solving of the problems!!

I found a huge mistake in solving the following problem. The biggest problem was that I couldn't correct it, because the issue was closed. So, I'll try to solve it right, in this post!

cos (x)+cos(3x)+cos(5x)=0

The first and huge mistake was that the teacher proposed to group cos (x)+cos(5x) and to transform the group also in a sum!!! Totally wrong!!!

**PAY ATTENTION!**

The right form is to transfor the SUM into a PRODUCT!!!

cos (x)+cos(5x)=2cos[(x+5x)/2]cos[(x-5x)/2]

cos (x)+cos(5x)=2cos3xcos2x

The rest of the problem is solved into another later question!!!

### 5 Answers | Add Yours

Interesting--the question I referenced above which had the wrong answer for part three has since been edited and corrected...guess the answerer noticed my response!

I wouldn't go for opening answers up to anyone to edit. What you need to do when you think an answer is incorrect is to send a message to an enotes staff member, like Brandi or Scott. They will verify whether the answer is indeed incorrect and allow you to write a correct answer. They're very nice people, so don't be afraid to send them messages.

It seems that a nice update to e-notes would be for an edit option on closed answers. I have seen answers in the literature areas that were inaccurate or wrong, but there too, the questions are closed. Perhaps if there were an edit option for closed questions, then the corrections could be made and the e-note facilitators could then use that information to verify the accuracy of answers before awarding points to the incorrect answer and witholding points from those who could clear up the error.

I had a similar issue last spring. It was also in math, and it wasn't that the given answer was wrong, but that I had another, and I thought more elegant solution. But the question had been closed. I believe I dealt with it exactly as you did--creating a discussion topic.

The other day, there was a 3 part math question in which the first two parts had major typos. I answered the third part, and when I checked back someone else had posted answers to all three parts (making the logical assumption of what the typos in the first two parts were.) The problem was, however, that their answer to part 3 was incorrect--my answer now appeared after it, and may have looked like a correction though it wasn't worded that way. But it made me think that maybe there should be better checking of answers by eNotes, somehow.

Thank you for your advice!