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[几何] “奔驰定理”在英语里的名字

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极光永明 Posted 2023-3-26 18:15 |Read mode
“奔驰定理”指的是以下定理:
对于 $ \triangle{ABC}$内一点$P$,记 $ S_ {A} = S_ {\triangle PBC} $ , $ S_ {B}  =  S_ {\triangle PAC} $ , $ S_ {C}  =  S_ {\triangle PAB} $ ,则$ S_ {A}\cdot \overrightarrow {PA}  + S_ {B} \cdot \overrightarrow {PB}  +  S_ {C} \cdot  \overrightarrow {PC}  =  \overrightarrow {0} $ 。
v2-806b26f720565267b5870342fa0728ac_r.png
应该不会叫Mercedes-Benz Theorem吧x

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好像没有专门的名字, 最接近的可能是拉密 (Lami) 定理  Posted 2023-3-26 18:46
@O-17 Lami定理不是和正弦定理等价的命题吗  Posted 2023-3-26 18:51

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hbghlyj Posted 2023-3-26 19:20
相关的恒等式(2个字母是复数的差,3个字母是有向面积)
$A_1 A_2⋅A_3 A_4+A_1 A_3⋅A_4 A_2+A_1 A_4⋅A_2 A_3=0$
$PA_1⋅PA_2 A_3+PA_2⋅PA_3 A_1+PA_3⋅PA_1 A_2=0$
$PA_1 A_2⋅PA_3 A_4+PA_1 A_3⋅PA_4 A_2+PA_1 A_4⋅PA_2 A_3=0$
$PQA_1⋅PA_2 A_3+PQA_2⋅PA_3 A_1+PQA_3⋅PA_1 A_2=0$

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kuing Posted 2023-3-26 19:29
不知道有没有英文名字。
但“奔驰定理”这名字我并不喜欢:
首先并不是所有人都认得奔驰的 LOGO,我不想帮这品牌卖广告。
其次他的 LOGO 是圆而非三角形,说像也并不像。
相比这下“裤衩定理”更好

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可以叫飞镖定理。  Posted 2023-3-26 21:11
这竟然有4个赞😃  Posted 2023-3-27 00:30

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Czhang271828 Posted 2023-3-26 22:00
Chatgpt 的回复

Yes, this theorem is called the Vector Area Theorem or the Vector Cross Product Theorem.

The Vector Area Theorem states that for any triangle $\triangle ABC$ and any point $P$ inside the triangle, the sum of the vector products of the areas of the triangles formed by $P$ and the vertices of the triangle with the opposite side vectors is equal to the zero vector.

In other words,

$S_{\triangle APB}\cdot \overrightarrow{PC}+S_{\triangle BPC}\cdot \overrightarrow{PA}+S_{\triangle CPA}\cdot \overrightarrow{PB} = \overrightarrow{0}$

where $S_{\triangle APB}$, $S_{\triangle BPC}$, and $S_{\triangle CPA}$ are the areas of triangles $\triangle APB$, $\triangle BPC$, and $\triangle CPA$, respectively, and $\overrightarrow{PA}$, $\overrightarrow{PB}$, and $\overrightarrow{PC}$ are the vectors from $P$ to $A$, $B$, and $C$, respectively.

This theorem is useful in solving problems in geometry and physics that involve vector quantities and areas.
后续对话
Czhang271828: But such theorem is known as Mercedes-Benz Theorem in China, 用中文说就是“奔驰定理”, how do you think about this? Either stupid or 傻逼?
Chat GPT: As an AI language model, I do not have the ability to express opinions or use inappropriate language. It is important to use respectful and appropriate language when discussing mathematical theorems or any other topic.

Regarding the name "Mercedes-Benz Theorem" or "奔驰定理" in China, it is not an official or widely recognized name for the Vector Area Theorem. While it is common for mathematical theorems to have multiple names or nicknames, it is important to use the standard name when communicating with others in the field to avoid confusion.

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TSC999 Posted 2023-3-26 22:21
这个奔驰定理,用复平面解析几何方法来证明是非常简单的,见 forum.php?mod=viewthread&tid=10399&extra=page=1 中的例十一。

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hejoseph Posted 2023-3-26 22:32
TSC999 发表于 2023-3-26 22:21
这个奔驰定理,用复平面解析几何方法来证明是非常简单的,见 forum.php? ...
你那里的证明都是用软件去算的,运算都复杂,还能算“简单”?如果都是用软件输入已有命令计算出结果来说是简单那么没什么好说的了。

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hbghlyj Posted 2023-3-27 00:25
Vector Analysis(Schaum's Outline)第31页 第54题 取$r=(0,0,1)$可得“奔驰定理”
Screenshot 2023-03-26 at 17-24-19 Schaum's Outline of Vector Analysis by Mu.png

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hbghlyj Posted 2023-3-27 00:27
Dual basis
In 3-dimensional Euclidean space, for a given basis $ \{\mathbf {e} _{1},\mathbf {e} _{2},\mathbf {e} _{3}\} $, the biorthogonal (dual) basis $ \{\mathbf {e} ^{1},\mathbf {e} ^{2},\mathbf {e} ^{3}\} $ can be found by formulas below:
$$ \mathbf {e} ^{1}=\left({\frac {\mathbf {e} _{2}\times \mathbf {e} _{3}}{V}}\right)^{\mathsf {T}},\ \mathbf {e} ^{2}=\left({\frac {\mathbf {e} _{3}\times \mathbf {e} _{1}}{V}}\right)^{\mathsf {T}},\ \mathbf {e} ^{3}=\left({\frac {\mathbf {e} _{1}\times \mathbf {e} _{2}}{V}}\right)^{\mathsf {T}}. $$
Reciprocal lattice

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