设α∈（0,π/3) β∈（π/6,π/2) 且5/3sinα+5cosα=8 ,/2sinβ+/6cosβ =2 求cos（α+β ）设α∈（0,π/3) β∈（π/6,π/2) 且5/3sinα+5cosα=8 ,/2sinβ+/6cosβ =2 求cos（α+β ）的值且5√3sinα+5cosα=8 ,√2sinβ+√6cosβ =2看

设-π/6 设3π/4 设-3π 设3π 设π/3 设π 设-π 设π 设π 设sinα=12/13,cosβ=-3/5,α,β∈(0,π)求cos(α-β) 设α∈(0,π),sinα-cosα=-1/3,求cos2α 设α∈(0,π),sinα-cosα=-1/3,求cos2α 设α,β满足条件-π/2 设α,β满足条件-π/2 设α、β∈（-π/2,π/2）,那么“α 设α∈(-π/2,0),cosα=1/2,则tan(α+π/6)= 设α∈(0,π/2),若sinα=4/5,则cos(α-π/3)等于? 设x=cosα α∈[-π/6,2π/3]则arcsinx的取值范围