Ω:p²≤z≤1
0≤p≤1
0≤θ≤2π
原式=∫∫∫ p·pdpdzdθ
=∫(0,2π)dθ∫(0,1)p²dp∫(p²,1)dz
=2π ∫(0,1)p²(1-p²)dp
=2π(p³/3-p^5/5)|(0,1)
=2π·(1/3-1/5)
=4π/15
Ω:p²≤z≤1
0≤p≤1
0≤θ≤2π
原式=∫∫∫ p·pdpdzdθ
=∫(0,2π)dθ∫(0,1)p²dp∫(p²,1)dz
=2π ∫(0,1)p²(1-p²)dp
=2π(p³/3-p^5/5)|(0,1)
=2π·(1/3-1/5)
=4π/15