Biaxial Moment of Area

I_{yz} = - \frac{1}{24} \cdot \sum_{i = 1}^{n} (y_{i} \cdot (3 \cdot {z_{i}}^{2} + 2 \cdot z_{i} \cdot z_{i - 1} + {z_{i - 1}}^{2}) + y_{i - 1} \cdot ({z_{i - 1}}^{2} + 2 \cdot z_{i} \cdot z_{i - 1} + {3 \cdot z_{i - 1}}^{2})) \cdot (y_{i} - y_{i - 1})

y	y-coordinate of the polygon point
z	z-coordinate of the polygon point

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