+1124 
Hi good people,
Please help me with this one...It must be proved that SWTD is a quadrilateral. I have mangaed to see a few things, which I dotted down, but fail to get the full picture. I was trying to prove SDW=STW...that would do it, or prove oposite angle to be 180 deg....I just do not see it...please help..thank you very much!
