阿呆591的博客

目录摘要1. 勾股定理摘要本专栏收录初中数学中，个别习题的个人解答（不定期更新）1. 勾股定理[人教版,P29,14P_{29},14P29​,14] 如图111，△ACB\triangle ACB△ACB和△ECD\triangle ECD△ECD都是等腰直角三角形，CA=CB，CE=CDCA=CB，CE=CDCA=CB，CE=CD，△ACB\triangle ACB△ACB的顶点AAA在△ECD\triangle ECD△ECD的斜边DEDEDE上。求证:AE2+AD2=2AC2(1)AE

关于类间方差和类内方差，总方差关系的证明对于给定的数据样本，将其分为两类:AAA和BBB。若记总方差为σtotal2\sigma_{total}^2σtotal2​，类内方差和为σintra2\sigma_{intra}^2σintra2​和类间方差和为σinter2\sigma_{inter}^2σinter2​，那么下式成立：σtotal2=σinter2+σintra2(1)\sigma_{total}^2 = \sigma_{inter}^2 + \sigma_{intra}^2 \tag{