ثابت الالتواء: الفرق بين النسختين

<math>J_{zz} = J_{xx}+J_{yy} = \frac{\pi r^4}{4} + \frac{\pi r^4}{4} = \frac{\pi r^4}{2}</math><ref name="Weisstein, Eric W.">"Area Moment of Inertia." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/AreaMomentofInertia.html {{Webarchive|url=https://web.archive.org/web/20200318192849/https://mathworld.wolfram.com/AreaMomentofInertia.html |date=18 مارس 2020}}</ref>