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§4.1 圆的周长

§4.1 圆的周长. 两辆遥控模型赛车分别沿着边长为 3 米的正方形和直径为 3 米的圆形塞道进行比赛,如果它们同时,同速从同一地点出发,那么谁先回到原出发点呢?. 3. 3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14. 1 2 3 4 5 6 7 8 9 10 11 12 13.

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§4.1 圆的周长

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  1. §4.1 圆的周长 两辆遥控模型赛车分别沿着边长为3米的正方形和直径为3米的圆形塞道进行比赛,如果它们同时,同速从同一地点出发,那么谁先回到原出发点呢? 3 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14

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  3. 用字母C表示圆的周长,d表示直径,r表示半径 ,那么 C=πd或 C=2πr 说明:在这个公式中,两个量是变化的。即周长和直径或半径 例题1:一张王莲的叶子近似一个圆,它的直径约是0.95米,这张叶子的周长是多少米?(结果保留两位小数) 解:d=0.95. C=πd=3.14×0.95=2.983 2.98(米) 答:这张叶子的周长约是2.98米。

  4. 例题2:一颗卫星围绕地球飞行,飞行轨道近似圆形。已知卫星距离地球表面例题2:一颗卫星围绕地球飞行,飞行轨道近似圆形。已知卫星距离地球表面 500千米,飞行了14圈,问卫星一共飞行了多少千米?(地球的半径约 6400千米) 解:R轨=500+6400=6900 C轨=2πR轨=2×3.14×6900=43332 14 C轨=43332×14=606648(千米) 答:卫星绕地球一周一共飞行了606648千米。

  5. 例题3:如图,如果圆环的外圆周长C1 250厘米,内圆周长C2 = =150厘米 r R o 球圆环的宽度d(精确到0.1厘米) d d

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