題目 Problem Part I Multiple Choice Consider the spherical coordinates system x=ρsinϕcosθx=\rho\sin\phi\cos\thetax=ρsinϕcosθ, y=ρsinϕsinθy=\rho\sin\phi\sin\thetay=ρsinϕsinθ, and z=ρcosϕz=\rho\cos\phiz=ρcosϕ. The volume element dV=dx dy dz\mathrm{d}V=\mathrm{d}x\,\mathrm{d}y\,\mathrm{d}zdV=dxdydz can be changed as (A) ρsinϕ dρ dθ dϕ\rho\sin\phi\,\mathrm{d}\rho\,\mathrm{d}\theta\,\mathrm{d}\phiρsinϕdρdθdϕ. (B) ρcosϕ dρ dθ dϕ\rho\cos\phi\,\mathrm{d}\rho\,\mathrm{d}\theta\,\mathrm{d}\phiρcosϕdρdθdϕ. (C) ρ2sinϕ dρ dθ dϕ\rho^2\sin\phi\,\mathrm{d}\rho\,\mathrm{d}\theta\,\mathrm{d}\phiρ2sinϕdρdθdϕ. (D) ρ2cosϕ dρ dθ dϕ\rho^2\cos\phi\,\mathrm{d}\rho\,\mathrm{d}\theta\,\mathrm{d}\phiρ2cosϕdρdθdϕ. 解答