點解做chain rule,integration by sub , differential equations 嘅時候dy/dx可以拆開做分數 明明有啲書話dy/dx is not a fraction
technically唔當係fraction
只係idea上係,同埋好多property似
實際上要嚴謹prove chain rule,牽涉好多細節
想知再講
想知快講
你仲讀得熟過我啦
點解做chain rule,integration by sub , differential equations 嘅時候dy/dx可以拆開做分數 明明有啲書話dy/dx is not a fraction
technically唔當係fraction
只係idea上係,同埋好多property似
實際上要嚴謹prove chain rule,牽涉好多細節
想知再講
想知快講
點解做chain rule,integration by sub , differential equations 嘅時候dy/dx可以拆開做分數 明明有啲書話dy/dx is not a fraction
technically唔當係fraction
只係idea上係,同埋好多property似
實際上要嚴謹prove chain rule,牽涉好多細節
想知再講
想知
點解做chain rule,integration by sub , differential equations 嘅時候dy/dx可以拆開做分數 明明有啲書話dy/dx is not a fraction
technically唔當係fraction
只係idea上係,同埋好多property似
實際上要嚴謹prove chain rule,牽涉好多細節
想知再講
想知
咁好奇真係少見
Idea上,
dy/dx可以睇成(small in y change) / (small x change)
留意,(small in y change)係dependent on (small x change)
例如y=2x, 係可以用2(x+0.0001) / (2x)去估算dy/dx
但實際上原本定義果種small係所謂infinitesimal,係細到「你想幾細仲會更細」,只係一個抽象既概念。如果你定死左幾細(如例子small x change=0.0001),得出既只係估算
因為呢個idea,所以好多類似fraction既特性佢都有。
Technical上,我用chain rule既proof做例子,只睇會頭暈,最好搵D紙寫下
以下我會寫兩個proof
一個可以描述idea,但有漏洞
一個係真proof,避開除法,但有少少長
真Proof唔明唔緊要,因為要做開數學先明入面個思維
我當我想求g(f(x))係x=c既微分
Let y=f(x),z=g(y)=g(f(x))
d=f(c)
[ig]https://na.cx/i/YUiH9s5.jpg[/mg]
呢個proof係將 (change in z) / (change in x)
寫做 (change in z) / (change in y) * (change in y) / (change in x)
exactly就係上面個idea,不過要take limit之前做
咁做係最簡單直接,亦係大部份書既proof,雖然唔係好rigorous。因為萬一(change in y)=0,會有問題
要construct一個真proof,就要用到一個LEMMA
[ig]https://na.cx/i/goaR3Eg.jpg[/img]
如果f'(c)存在,則:
存在某phi(x),使得f(x)-f(c)=phi(x) (x-c),而phi(x)會cts(continuous) at c,phi(c)=f'(c)
利用呢個LEMMA,我地可以以乘避除
[im]https://na.cx/i/4Q8WN9Y.jpg[/img]
將g(f(x))-g(f(c))好既樣先,再除以x-c,最後take limit
geometric 問唔問得
oblique cone parametric equation 係點搵?
呢題我又未遇過,你有咩條件比左?
最直接係寫左一般cone條式,再將條式用rotation matrix將d variable rotate
http://mathworld.wolfram.com/Cone.html
呢到有standard(right) cone parametric equation,咁個尖尖就同個底個圓既圓心同軸,而家我想搵個尖尖座標唔同CONE 底個圓心同軸既parametric equation
另外搵到既話,我仲想問cone 個開口有無得控制(依家係由height ⊂ (0,h) 都係2π,我想知有無得[0,2π]咁變
樓主教唔教到大學工程嘅數
記得仲係學生果時有條問
Proof the Earth cannot be displayed on a map without distortion.
好深刻
記得仲係學生果時有條問
Proof the Earth cannot be displayed on a map without distortion.
好深刻
忘記晒~~
以前好似識做
記得仲係學生果時有條問
Proof the Earth cannot be displayed on a map without distortion.
好深刻
忘記晒~~
以前好似識做
係咪assume左地球係圓
記得仲係學生果時有條問
Proof the Earth cannot be displayed on a map without distortion.
好深刻
忘記晒~~
以前好似識做
係咪assume左地球係圓
yes
記得仲係學生果時有條問
Proof the Earth cannot be displayed on a map without distortion.
好深刻
忘記晒~~
以前好似識做
係咪assume左地球係圓
yes
點解做chain rule,integration by sub , differential equations 嘅時候dy/dx可以拆開做分數 明明有啲書話dy/dx is not a fraction
technically唔當係fraction
只係idea上係,同埋好多property似
實際上要嚴謹prove chain rule,牽涉好多細節
想知再講
想知
咁好奇真係少見
Idea上,
dy/dx可以睇成(small in y change) / (small x change)
留意,(small in y change)係dependent on (small x change)
例如y=2x, 係可以用2(x+0.0001) / (2x)去估算dy/dx
但實際上原本定義果種small係所謂infinitesimal,係細到「你想幾細仲會更細」,只係一個抽象既概念。如果你定死左幾細(如例子small x change=0.0001),得出既只係估算
因為呢個idea,所以好多類似fraction既特性佢都有。
Technical上,我用chain rule既proof做例子,只睇會頭暈,最好搵D紙寫下
以下我會寫兩個proof
一個可以描述idea,但有漏洞
一個係真proof,避開除法,但有少少長
真Proof唔明唔緊要,因為要做開數學先明入面個思維
我當我想求g(f(x))係x=c既微分
Let y=f(x),z=g(y)=g(f(x))
d=f(c)
[ig][url]https://na.cx/i/YUiH9s5.jpg[/mg][/url]
呢個proof係將 (change in z) / (change in x)
寫做 (change in z) / (change in y) * (change in y) / (change in x)
exactly就係上面個idea,不過要take limit之前做
咁做係最簡單直接,亦係大部份書既proof,雖然唔係好rigorous。因為萬一(change in y)=0,會有問題
要construct一個真proof,就要用到一個LEMMA
[ig][url]https://na.cx/i/goaR3Eg.jpg[/img][/url]
如果f'(c)存在,則:
存在某phi(x),使得f(x)-f(c)=phi(x) (x-c),而phi(x)會cts(continuous) at c,phi(c)=f'(c)
利用呢個LEMMA,我地可以以乘避除
[im][url]https://na.cx/i/4Q8WN9Y.jpg[/img][/url]
將g(f(x))-g(f(c))好既樣先,再除以x-c,最後take limit
thanks 巴打,好有心
成日唔識諗個triple integral coordinate angle range
見過兩種polar coordinate
我建議extend 2D果隻版本~
x-y plane theta照KEEP
再加個inclination angle phi由-90去到90度
好好記
唔識由equation睇
同埋係咪要幻想個3d figure
記得仲係學生果時有條問
Proof the Earth cannot be displayed on a map without distortion.
好深刻
忘記晒~~
以前好似識做
係咪assume左地球係圓
yes
係咪又係d咩 gaussian curvature 唔同跟住無local isometry
咩係differential form 有咩用
咩係differential form 有咩用
如何搵non symmetrical matrix 的 eigenvalue ?