Edited below
Try to follow the figures I'm describing. I drew an isosceles triangle, base 11.4, height 2.8. Then I dropped a line from the top straight down to the base so there are 2 right triangles. With the bottom side 5.7 and the side perpendicular to that 2.8. Put your trig skills to work and find the angle between the 5.7 side and the hypotenuse.
Now take one of those right triangles and tip it so the hypo9tenuse is vertical. That's the limit to how far it can be tipped before it topples. So, the amount you tipped your figure is the angle you found above.
Oooops!! After getting some sleep I sat down at the computer, saw the figures I sketched last night, and realized I told you wrong. Call the angle you found above theta. You have to tip it 90-theta to get the hypotenuse vertical..