a⊥b,则a*b＝0|a-b|^2＝(a-b)*(a-b)＝|a|^2+|b|^2＝5+1＝6,|a-b|＝√6|a+tb|^2＝(a+tb)*(a+tb)＝|a|^2+t^2×|b|^2＝5+t^2,|a+tb|＝√(5+t^2)(a-b)*m＝(a-b)*(a+tb)＝|a|^2-t|b|^2＝5-ta-b与m的夹角为π/4,则cos(π/4...