How I tried to derive the formula for the sine of sum on my own …

One evening I just got interested in this formula. But my school notes were not reachable at the moment and I did not want to look for it in the internet. And also maybe I wanted to prove something to myself. Either way I want to show you here the results. I have spent a lot of time solving this and it is a little embarrassing :), but still.


This solution is not finished. The cases when the angles are situated on the different sides from 90 degrees axis should be also considered.

The following is my first attempt to solve this,so if you are not interested, you can skip it ...






And also the cases when one of the cosines or both sines of the angles are zero should be considered separately.

I do not imply in any way that this is my invention, just the way I would use if I had to derive these relations.

LAN printing problem on ubuntu 9.04

I cannot print .pdf documents using Document viewer via LAN printer(that is not attached directly to my computer). All the time I get "Failed to print document". But printing .doc files and .txt works ok. So it is obvious that the problem is in the viewer. And indeed I can print pdfs using xpdf. Hope this tip will save somebody's time))