Assuming a freely jointed polymer chain that follows the Gaussian distribution as the probability function please prove. 2> = nl²

W(x,y,z)=(21)3e2(x2+y2+z2),where=(2nl23)21Letr2=x2+y2+z2W(r)dr=W(x,y,z)(4r2)drW(r)=4(21)3r2e2r2W(r)dr=1r2W(r)dr=R2