Triangle #1
c = 5.000

Triangle #2
a = 6.708

Triangle #3
Impossible.

Triangle #4
c = 17.263

Triangle #5
c = 2036.666

Triangle #6
c = 1.414

Triangle #7
a = 4.000

Triangle #8
a = 237.167

Triangle #9
Impossible.

Triangle #10
b = 5.657

Triangle #11
b = 309.839

Triangle #12
Impossible.