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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,半径,直径,轴对称,无数,直径,3,d,2 r,r,2,3,3,9,3,0.785dm,1/4,0.6,8,6.28,4,18.84,厘米,28.26,厘米,2,0.785dm,2,可以用,举例子,方法,d=1x2,=2cm,c=2x3.14x1,=6.28,s=3.14x12,=3.14 cm,2,r=1,r=1x3,=,3,cm,d=3x2,=6cm,c=2x3.14x3,=18.84,s=3.14x3,2,=28.26cm,2,扩大的倍数,d=6 2,=,3,C=18.84 6.28,=,3,s=28.263.14,=,9,第,4,小题：,6cm,从这个图可得知：,6,厘米,既是正方形的,边长,又是圆的,直径,所以：,r=62=3cm,c=3.14x6=18.84,cm,s=3.14x3,2,=28.26,cm,2,第,5,小题,周长,=3.14cm,正方形的边长,=,周长,4=3.14,4=0.785(cm),圆的半径（,r,）,=,周长,圆周率,2,=3.14,3.14,2=,0.5cm,圆的面积,(s)=3.14x,（,0.5,）,2,=,0.785cm,2,第,6,小题,周长,=3.14cm,小圆,大圆,大圆是小圆的,小圆是大圆的,d=2x2,=4cm,c=2x3.14x2,=12.56,s=3.14x2,2,=12.56 cm,2,r=2,r=8,2,=4cm,d=8cm,c=2x3.14x4,=25.12,s=3.14x4,2,=50.24cm,2,d=8 4,=,2,C=25.12 12.56,=,2,s=50.2412.56,=,4,第,7,小题：,或,1/2,或,1/2,或,1/4,结论,可以用,举例子,方法,d=1cm,1,圈,=3.14x1,=3.14,25.12,3.14=,8,圈,后轮,前轮,d=1x,2,=2cm,1,圈,=3.14x2,=6.28,4,圈,=6.28x,4,=25.12cm,后轮直径是前轮的,2,倍,后轮的周长是前轮的,2,倍，也就是说,后轮滚动,1,圈，前轮需滚动,2,圈,后轮滚动,4,圈，前轮需滚动,8,圈,第,9,小题：,结论,可以用,举例子,方法,r=2cm,c=2x3.14x2,=12.56,小圆,大圆,r=1cm,c=2x3.14x1,=6.28,半径相差,1,厘米,周长相差,=,12.56 6.28=6.28,厘米,第,10,小题：,x,x,x,B,A,D,D,C,A,r=1.5cm,d=3cm,o,5x2=,10m,3.14x10=,31.4m,3.14X5,2,=,314m,2,0.8,2=,0.4dm,3.14x0.8=,2.512dm,3.14X0.4,2,=,0.5024dm,2,18.84,3.14,2=,3cm,18.84,3.14=,6cm,3.14X3,2,=,28.26cm,2,3.14x24,2,=37.68cm,37.68+24=61.68cm,2x3.14x5,4,=7.85cm,7.85+5+5=17.85cm,长方形面积,2,个半圆的面积,长方形的面积,圆的面积,长方形面积,=120 x50=6000dm,2,圆形面积,=3.14x,（,502,）,2,=1962.5dm,2,阴影面积,=6000-1962.5=4037.5dm,2,大圆面积的,1/2,小圆面积的,1/2,大圆的半径,=8,2=4m,小圆的半径,=42=2m,大圆面积的,=3.14x4,2,x =25.12m,2,小圆面积的,=3.14x2,2,x =6.28m,2,阴影面积,=25.12-6.28=18.84m,2,r=28.23.142=4.5m,s=3.14x(4.5),2,=3.14x20.25=63.585m,2,周长,=2,条长,+,圆周长,=100+100+3.14x64=200+200.96=400.996m,面积,=,长方形面积,+,圆面积,=100 x64+3.14x32,2,=6400+3215.36=9615.36m,2,r=642=32m,1,圈,=3.14x66=207.24cm,1,分钟,=100,圈,=207.24x100=20724cm,2000m=200000cm,200000,20724,9.7,（分）,大圆的半径,=4+2=6m,水池面积,=3.14x4,2,=50.24m,2,小路面积,=113.04-50.24=62.8m,2,外圆面积,=3.14x6,2,=113.04m,2,水池,小路,6,米,滚动,1,周,6,米,路面,前进的米数,前进的米数就是,圆的周长,=3.14x1=3.14m,1,米,路面面积就是,长方形的面积,=3.14x6=18.84m,2,r,r,阴影面积,=,半圆面积,-,三角形面积,半圆面积,=,x,rxr,2=3.14x9,2=14.13cm,2,r,阴影面积,=14.13-9=5.13cm,2,三角形面积,=,底,x,高,2=2xrxr,2=9,2xrxr,2=9cm,2,rxr,=9cm,2,
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