(1)sinαcosβ+cosαsinβ=sin(α+β)∈[-1,1]∴ (1/2)+cosαsinβ∈[-1,1]∴ cosαsinβ∈[-3/2,1/2](2)sinαcosβ-cosαsinβ=sin(α-β)∈[-1,1]∴ (1/2)-cosαsinβ∈[-1,1]∴ cosαsinβ∈[-1/2,3/2]综上 cosα...