题目先化简,再求代数式1a−2÷(1+1a−2\frac{1}{{a-2}}\div (1+\frac{1}{{a-2}}a−21÷(1+a−21）的值,其中a=2sin60∘+3tan30∘a=2\sin 60^{\circ}+\sqrt{3}\tan 30^{\circ}a=2sin60∘+3tan30∘.知识点：分式的化简求值章节：未标注
