根號(hào)下[(a^2+b^2+c^2)/2]
設(shè)長(zhǎng)寬高為m,n,p
m^2+n^2=a^2
m^2+p^2=b^2
n^2+p^2=c^2
長(zhǎng)方體的對(duì)角線＝根號(hào)下(m^2+n^2+p^2)
上面三個(gè)式子相加,
2(m^2+n^2+p^2)=a^2+b^2+c^2
所以,對(duì)角線＝根號(hào)下[(a^2+b^2+c^2)/2]