等腰梯形有且只有一条对称轴,等腰梯形的对称轴是经过两底中点的直线。
对称轴是使几何图形成轴对称或旋转对称的直线。对称图形的一部分绕它旋转一定的角度后,就与另一部分重合。 许多图形都有对称轴。例如椭圆、双曲线有两条对称轴,抛物线有一条。正圆锥或正圆柱的对称轴是过底面圆心与顶点或另一底面圆心的直线。
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/0eb30f2442a7d9331ca6d723a24bd11373f00157?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
扩展资料:
在以下两种情况下周长公式分别为:
1、已知上底、下底、腰,计算周长
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/95eef01f3a292df5d0efc17bb3315c6034a873ab?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
2、已知上底、下底、高,计算周长
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/bd3eb13533fa828bec7eff8df21f4134970a5a7a?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
对于情况1,根据周长定义可直接得到。
对于情况2,由于等腰梯形的腰长度未知,首先需求腰的长度。根据勾股定理,可求得腰长为:
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/b03533fa828ba61ee3b3aa414e34970a304e597a?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)