Choosing Redundant Forces for Structural Stability?

[fonseh]

Homework Statement

In this example , the author said that we can choose either G or E as redundant and ignore the force when we are doing the analysis ...
I was told by my lecturer that when we are choosing the redundant forces , it''s important that after removing the redundant force , the whole structure remain stable .

Homework Equations

The Attempt at a Solution

Hoewever , I think that we can choose the force at E as redudant and remove it when we are doing the analysis. This is because by doing so , the whole structure would become unstable . So , I think we can only choose the support at G as redundant force

 

[John Morrell]

Why would removing E make it unstable? If you remove E, the pin at A would be 'pulled' upwards and the support at G would have a greater weight on it. That's not unstable at all.