=5dm,周长=2π×5=10π=31.4(dm),面积=π×5²=25π=78.5(dm²)d=6cm,周长=π×6=6π=18.84(cm),面积=1/4×π×6²=9π=28.26(cm²)1.正方形的内切圆,直径等于边长,所以半径r=2m.花池面积为πr²=4π.花坛面积为4×4=16,所以比值为4π:16=π:4=0.785
2.大圆的面积减去小圆的面积
π(50+2)² - π50² =204π=640.56(m²)
=5dm,周长=2π×5=10π=31.4(dm),面积=π×5²=25π=78.5(dm²)d=6cm,周长=π×6=6π=18.84(cm),面积=1/4×π×6²=9π=28.26(cm²)1.正方形的内切圆,直径等于边长,所以半径r=2m.花池面积为πr²=4π.花坛面积为4×4=16,所以比值为4π:16=π:4=0.785
2.大圆的面积减去小圆的面积
π(50+2)² - π50² =204π=640.56(m²)