Tests are passable in C and C++ without even declaring floats

Yes thank you. That test is useless or should be True. You can make the angle between 1 and 2 wider enough until line 3 builds a triangle. This kata is not well built. The only way to solve this kata is to modify the solution until you trick all the tests.

(In this case, all triangles must have surface greater than 0 to be accepted).

It is perfectly possible: 68 guys passed the kata...

It should be helpful if you state which language and show your code (mark your post as having spoiler content). Otherwise there is nothing we can do to help you.