Bilingual geometry notebook 双语几何笔记

I will update this notebook at least once per month, with formulae, techniques and proofs.
这篇笔记每月至少会更新一次，内容包括公式，证明，解题技巧。

Geometric measuring 几何度量
- 1.1 2D shapes 二维图形
  1.1.1 area 面积
  1.1.2 perimeter 周界
- 1.2 3D shapes 三维立体
  1.2.1 volume 体积
  1.2.2 surface area 表面积
Trigonometry 三角学
- 2.1 trigonometric functions 三角函数
  2.1.1 definition and special values 定义和特殊值
  2.1.2 trigonometric identities 三角学定律
- 2.2 the centres of a triangle 三角形的“心”
Parallel & perpendicular & lines & angles 平行，垂直，线，角
- 3.1 2D 二维
  3.1.1 parallel 平行
Cartesian coordinate geometry 解析几何

#Geometry

Easy Math Editor

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Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$