∵sinα=√10/5,cosβ=√10/10∴cosα=√15/5,sinβ=3√10/10sin(α-β)=sinαcosβ-cosαsinβ=(√10/5)(√10/10)-(√15/5)(3√10/10)=1/5 - 3√6/10＜0∵0＜α＜π/2 ,0＜β＜π/2 ∴-π/2＜α-β＜π/2∴α-β=ar...