12ab(π+2)\frac{1}{2} a b(\pi+2)21ab(π+2)
ab(π−1)a b(\pi-1)ab(π−1)
14ab(π−2)\frac{1}{4} a b(\pi-2)41ab(π−2)
14(π+2)\frac{1}{4}(\pi+2)41(π+2)