求圆的面积 1.已知r=1cm S= 2.已知r=3cm S= 3.已知d=8cm S= 4.已知d=10cm S= 5.已知r=6cm S=

.r=1cm S=π=3.14
2.已知r=3cm S= 3²π=9π=28.26
3.已知d=8cm S= (8/2)^2π=50.24
已知d=10cm S= (10/2)^2π=78.5
5.已知r=6cm S=6^2π=113.04
6.已知c=12.56cm S=(12.56/π/2)^2*π=4π=12.56
7.已知c=31.4cm S=(31.4/π/2)^2π=5^2*π=78.5
8.已知c=18.84cm S= (18.84/π/2)^2π=28.26
9.已知c=6.28 r= S=