内接正n变形,由n个三角形组成,顶点在圆心,圆心角2π/n,
三角形底是半径r,高是半径r乘sin(2π/n),面积(1/2)r²sin(2π/n),n个:
(nr²/2)sin(2π/n)
利用特殊极限lim(x-->0)sinx/x=1
lim(n-->∞)2π/n=0,把上面的x用2π/n代换,分子分母同时乘以2π/n,
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/d01373f082025aaf4fbbb129f0edab64024f1a43?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
追问“内接正n变形,由n个三角形组成”
为什么??
还有就是。。。。没懂
追答外接圆心连接各个顶点。
追问“lim(n-->∞)2π/n=0,把上面的x用2π/n代换,分子分母同时乘以2π/n,”
没懂啊。。。。
追答![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/472309f79052982238fde520dcca7bcb0b46d403?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/00e93901213fb80ef2aabe343dd12f2eb83894de?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/2934349b033b5bb5a890ff1d3dd3d539b700bc8a?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/d788d43f8794a4c2a65639c805f41bd5ac6e39d8?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/30adcbef76094b36d3ffc50ea8cc7cd98c109de0?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)