I have written solution that reached test 22 during the competition(I think it corresponds to 15th in offline mode) but now I have wa and i have run out of ideas. Can anyone give me a clue on this problem. Is there a problem with precision (I am making calculations with long double but use sqrt which is a bit unprecise).

As you can see in the sample output, precision of output is till six decimal points.
0.500000 -1.000000
Try to use long double and take care of some rounding errors. Hope it helps.
http://www.techcrashcourse.com/2015/03/c-program-to-calculate-area-of-parallelogram.html
http://www.techcrashcourse.com/2015/03/c-program-to-calculate-area-of-trapezium.html
http://www.techcrashcourse.com/2015/03/c-program-to-calculate-area-of-any-triangle.html