设0≤α≤β≤γ<π/2
1≥cosα≥cosβ≥cosγ>0
0≤sinα≤sinβ≤sinγ<1
sinα/cosβ+sinβ/cosγ+sinγ/cosα-tanα-tanβ-tanγ
=(sinα-sinβ)/cosβ+(sinβ-sinγ/cosγ+(sinγ-sinα)/cosα
≤(sinα-sinβ)/1+(sinβ-sinγ/1+(sinγ-sinα)/1
=0
所以……
设0≤α≤β≤γ<π/2
1≥cosα≥cosβ≥cosγ>0
0≤sinα≤sinβ≤sinγ<1
sinα/cosβ+sinβ/cosγ+sinγ/cosα-tanα-tanβ-tanγ
=(sinα-sinβ)/cosβ+(sinβ-sinγ/cosγ+(sinγ-sinα)/cosα
≤(sinα-sinβ)/1+(sinβ-sinγ/1+(sinγ-sinα)/1
=0
所以……