sin(β-α)=√10/10,
α,β为锐角,
cos(β-α)=√{1-[sin(β-α)]^2}=3/√10,
sinα=√5/5,
cosα=2/√5,
sinβ=sin(β-α+α)
=sin(β-α)*cosα+cos(β-α)*sinα
=√2/2.
β=45度.