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口算:,3.1412=,3.141.52=,3.1442=,3.1415=,3.1452=,3.1420=,3.1432=,3.1418=,37.68,28.26,47.1,7.065,62.8,78.5,50.24,56.52,求出下面图形的面积。,r = d2,S = r2,62 = 3(cm),3.1432 = 28.26(cm2),S = r2,3.1462 = 113.04(cm2),r =6cm,o,d=6cm,o,.,d=6cm,o,.,S = r2,3.1462 = 113.04(cm2),r = d2,62 = 3(cm),S = r2,3.1432 = 28.26(cm2),113.0428.26 = 74.78(cm2),r =6cm,o,d=6cm,o,.,S = r2,3.1462 = 113.04(cm2),r = d2,62 = 3(cm),S = r2,3.1432 = 28.26(cm2),113.0428.26 = 74.78(cm2),r =6cm,d=6cm,o,.,两个半径不相等的同心圆,就叫做圆环,也可以叫做环形。,求出下面图形的面积(单位:cm)。,.,8,7,求出下面图形阴影部分的面积(单位:dm)。,10cm,o,