扇形弧长×半径÷2=扇形纸片的面积,
2/9×π×半径÷2=1/9×π,
半径=R=1(cm),
扇形纸片的弧长:纸片所在圆的周长=圆心角:360°,
2π/9:2×R×∏=圆心角:360°,
2π/9:2×1×∏=圆心角:360°,
圆心角=360°×2π/9÷(2∏)
=40°