I need the angle from the triangle to the flat ground.
I assume I have to define two planes to work with which I can't find any info on for 3D planes. I got an equation from NoteMe:

Angle = inverse_cos((A * B) / (|A| * |B|))

I assume it is correct. A and B are planes and this equation will define the angle between the two planes, I just don't know how to define the planes from the points I have.