二、肌肉依收縮形式可分成兩大類，請寫出兩大類名稱並說明其定義（10%）

3.2. (4%) Suppose we have a thin (and uniform) disk with mass=m and radius=R (i.e., it has area density σ=m/(πR²)). For this disk, dm = σ*r*dr*dθ. The central moment of inertia I₃₃ is defined as ∫r² dm. (Integrate from θ=0 to θ=2π, and r=0 to r=R). Please calculate I₃₃ for the disk.