已知圆锥的底面直径为80cm，母线长90cm，求它的表面积和侧面展开图的圆心角．
直接写得数.+= 1﹣=+=﹣=++= 5÷8= 9.2×0.25×4= 0.8×25﹣10=
计算：．
直接写出下面各题的得数．= 21×4= 41÷7= 24÷5== 133×0= 103×5= 300×9= 1﹣=
计算下面各题．．
直接写得数+=+=+0.25=+= 1﹣=+﹣=
+
= 1﹣
=
+
=
﹣
=
+
+
= 5÷8= 9.2×0.25×4= 0.8×25﹣10=
．
= 21×4= 41÷7=
= 133×0=
=
．
+
=
+
=
+0.25=
+
= 1﹣
=
+
﹣
=
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