點用first principle D e^tanx
點用first principle D e^tanx
1) 乜野係random variable?
2) Proof T= Z / (U/k)^(1/2)
Z~N(0,1) & U~chi squared dist. with k degrees of freedom, where T is t distribution
Measurable function from sample space to R(or any measurable space S)
一般黎講,random variable係一個function將實驗結果轉化為另一個數字(或轉化為另一結果)
但呢個function既domain, target domain同埋function本身都要滿足某D條件,令我地measure probability既時候唔會出問題
而條件就係所謂Measurable function,即係pre-image of any measurable set is measurable
一般人可能難以理解,呢個世界上有一D event係無辦法測量(not measurable)。
我係[0,1]均勻分佈抽一個數字,果個數字係[1/2,1]入面既機率自然係1/2。但某D SET我係會講唔出,抽中係入面既機率係幾多。並唔係所有subset of [0,1]可以被測量機率
至於2,其實都係搵返佢個pdf就QED,但個PROOF太長,我SKETCH
將
T= Z / (U/k)^(1/2)
V= U
睇成係一個(Z,U)->(T,V)既transformation,用Jacobian 搵個jpdf
最後int 返T個marginal pdf,就會係t-distribution既pdf
喺probability, lebesgue measurability其實通常唔係重點(雖然當然重要)
event space可以理解做information,所謂嘅not measurable有時係可以理解做insufficient information
例子:有人擲兩粒骰,但唔話你知第二粒骰結果係乜。如果X代表第一粒嘅數字,Y代表第二粒,咁Y就唔係random variable,因為你根本冇Y嘅information
呢啲concept會喺conditional expectation用到
可唔可以教多少少double同triple integral點樣定個parametric representations?
認真唔撚識轉 唔撚明點做change of variables
equations of circles有咩重點
巴打有幫人補開習?
有嘅話telegram我 @kurdtkobain
可唔可以講下games theory
想自學
BFGS algorithm 比 DFP algorithm 有咩優勝之處?
點用first principle D e^tanx
攝兩個 tan (x + h) - tan x 分別做 e^tan x個 difference的分母同埋h的分子
講吓中學雞core prob
想問下functional analysis有咩applications? 同埋佢同variational calculus個functional有咩關係?
點解x=0 會叫做y=abs(x) 嘅sharp point?
想問下functional analysis有咩applications? 同埋佢同variational calculus個functional有咩關係?
樓主的post 大部份都係applied maths 層面...
如果同你講analysis 會唔會已經露餡?
A real function is borel measurable iff it is continuous?
一次問幾題得唔得