[x] unstable global structure if degree of external static determinacy < 0, and undeterminant if > 0. Only solve if = 0.
[x] unstable global structure if no joint equilibrium can be found on either of the supports. -> only happens when 2 of the 3 support reactions act in the same line.
[x] invalid inputs if inputs don't match (members start + members end, force indices + magnitudes + rotations, support indices + hor + ver + rotations, point indices (for supports, ext force, members) out of range).
[x] invalid structure: only designs with 2 supports are supported in the current version of the tool.
Solve Member Forces:
[x] same as for Solve Global Forces
[x] unstable internal structure if degree of internal static determinacy < 0, and undeterminant if > 0. Only solve if = 0.
Solve Global Forces:
Solve Member Forces: