Section Modulus at Point i About z-Axis

W_{z, i} = \frac{I_{y} \cdot I_{z} - {I_{yz}}^{2}}{I_{y} \cdot y_{i} - I_{yz} \cdot z_{i}}

I_y	Second moment of area about the y-axis
I_z	Second moment of area about the z-axis
I_yz	Centrifugal moment about the y- and z-axes
y_i	y-coordinate of Point i in the axis system y,z
z_i	z-coordinate of Point i in the axis system y,z

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