设0设0
设01、当cosa>0时 即a∈[0,π/2)∪(3π/2,2π]sina/cosa>√3∴ tana>√3 解π/3
是根号3*cosa,还是根号(3cosa)如果是前者,sina-跟号3*cosa=2(sinacos60-cosasin60)=2sin(a-60)>0a属于(π/3,4π/3)