Second moment of area of a hollow triangle

[Becky6]

Greetings!
Can someone please help me figure out how to calculate the second moment of area for a hollow isosceles triangle? Is there an equation available somewhere? Or can I simply subtract a smaller triangle from a larger one, using the equation I=bh³/36? (so I= b₁h₁³/36 -b₂h₂³/36)

Also, is there any way to account for the base wall being thicker than the sides?

Thank you!

 

[PhanthomJay]

Presumably you are looking for the area moment of inertia about the centroid of the hollow triangle. The subtractive method is ok. But it's not as simple as you indicate, because the centroid of each triangle do not share a common axis. You must first determine the centroid location of the hollow shape, then calculate the inertia of that shape using parallel axis theorem.