BGN-1.1.2

Formulae 公式

quadrilaterals 四边形

Refer to the last chapter for symbol representation.
字母含义见上一章。
Square and rhombus 正方形和菱形: $4s$
Rectangle and parallelogram 长方形和平行四边形: $2(a+b)$ ( $a$ and $b$ refer to the side length of two adjacent sides) （ $a$ 和 $b$ 分别指两相邻边的长度）

ellipticals 椭圆形

Call a circle’s circumference (perimeter) $C$ and diameter $d$ . Then $\pi =\dfrac {C}{d}$ , so $C=2\pi r=\pi d$ .
将一个圆的圆周和直径的长度分别称为 $C$ 和 $d$ 。易得 $C=2\pi r=\pi d$ 。

Techniques 技巧

When we meet irregular shapes, we can ‘move’ their perimeter without changing it’s value, as below.
当我们遇到不规则图形时，可以在不改边其周界长度当情况下边換其周界，如下。 Image 1.1.2-1 图1.1.2-1

Easy Math Editor

This discussion board is a place to discuss our Daily Challenges and the math and science related to those challenges. Explanations are more than just a solution — they should explain the steps and thinking strategies that you used to obtain the solution. Comments should further the discussion of math and science.

When posting on Brilliant:

Use the emojis to react to an explanation, whether you're congratulating a job well done , or just really confused .
Ask specific questions about the challenge or the steps in somebody's explanation. Well-posed questions can add a lot to the discussion, but posting "I don't understand!" doesn't help anyone.
Try to contribute something new to the discussion, whether it is an extension, generalization or other idea related to the challenge.
Stay on topic — we're all here to learn more about math and science, not to hear about your favorite get-rich-quick scheme or current world events.

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`bold` or `__bold__`	bold
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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}`	$\boxed{123}$

Comments

Jeff, this is good, but I don't understand Chinese.

Is there any other languages apart from Chinese and English that you can speak?

Yajat Shamji - 10 months, 2 weeks ago

Nope.

Jeff Giff - 10 months, 2 weeks ago

Sorry :/

Jeff Giff - 10 months, 2 weeks ago

That's okay.

Yajat Shamji - 10 months, 2 weeks ago

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}`	$\boxed{123}$