# Inertia, symmetry?

1. Mar 16, 2010

### rock.freak667

1. The problem statement, all variables and given/known data
I have to find the area moment of inertia about an axis 33 to the x-axis
http://img227.imageshack.us/img227/2392/shape.jpg [Broken]

2. Relevant equations
$$I_\phi=\frac{1}{2}(I_{xx}+I_{yy})+\frac{1}{2}(I{xx}-I_{yy})cos2\phi - I_{xy}sin2\phi$$

3. The attempt at a solution

I found Ixx, but since it is symmetrical, Ixx=Iyy, and since it is symmetrical about the x and y axes, Ixy=0

So the I about any axis is just the 1/2(Ixx+Iyy) = Ixx.

Is my thinking correct, or am I mistaking it?

Last edited by a moderator: May 4, 2017
2. Mar 16, 2010

### nickjer

Looks ok to me.