∵α、β是锐角,则00∵cosα=4/5,cos(α+β)=3/5∴sinα=√[1-(cosα)^2]=3/5sin(α+β)=√[1-(cos(α+β))^2]=4/5故sinβ=sin[(α+β)-α]=sin(α+β)cosα-cos(α+β)sinα=(4/5)(4/5)-(3/5)(3/5)=7/25....