Calculate the perimeter and the area of a circle skillfully 熟练地进行周长和面积的计算。
2.
Teacher : what is the area of a circle 师:什么是圆的面积?
3.
Review the knowledge about circles . further study the names of all the parts of a circle and how to work out the perimeter and the area of a circle 复习圆的有关知识,进一步熟悉了圆各部分的名称,以及圆周长和面积的计算方法。