(1)以点O为圆心,以4÷2=2厘米为半径的圆,如图所示:
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/14ce36d3d539b600f7eabb0ee450352ac65cb767?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
(2)周长:3.14×4=12.56(厘米);
面积:3.14×(4÷2)^2=3.14×22=3.14×4=12.56(平方厘米);
圆的面积是12.56平方厘米.
扩展资料
圆的周长公式
圆的周长:
圆周长的一半 c=πr
半圆的周长 c=πr+2r
圆的周长公式推导(此方面涉及到弧微分)
设圆的参数方程为
圆在一周内周长的积分
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/8601a18b87d6277f1655868125381f30e824fcc0?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
代入,可得
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/1ad5ad6eddc451dacb1ab852bbfd5266d116329e?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/a1ec08fa513d2697fd94bce458fbb2fb4216d8c0?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/b8389b504fc2d5627d8f6454ea1190ef77c66c80?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
即
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/5fdf8db1cb1349541b985cdd5b4e9258d0094a80?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
圆的面积公式
圆的面积计算公式:
或
圆的面积求直径:
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/a8773912b31bb05185b106913b7adab44bede0f6?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
把圆分成若干等份,可以拼成一个近似的长方形。长方形的宽相当于圆的半径。
圆锥侧面积
(l为母线长)
参考资料来源:百度百科:圆