7,652 reputation
821
bio website linkedin.com/in/gt6989b
location New York, NY
age 35
visits member for 3 years, 1 month
seen yesterday

Dec
10
comment Factoring a cubic polynomial?
the last row contains all zeroes except the last element, so that element $\lambda = -2$ must be an eigenvalue.
Dec
10
comment $f$ satisfies $|f(x)-f(y)|\ge \frac{1}{2}\cdot|x-y|$ , is $f$ onto?
@Did IMO this is enough hints for a full fledged answer...
Dec
10
comment How many rotations are there in $\mathbb R^3$ which take $C$ to itself?
Please add your approach to the problem and we will be glad to provide hints.
Dec
9
comment Just a basic limit of a function
The answer is $1/2$ but it takes 2 L'Hospital applications. Not sure how to do this without Taylor or L'Hospital...
Dec
9
comment With “per partes” (by parts) derive a recurrent formula for the calculation of the integral
Does this need a homework tag? What did you try to solve this problem?
Dec
9
comment A “What's my vector?” game
So what is the metric which you are using to compare strategies? Best case? Worst case? Average case? If average, do you assume each input from Alice has equal weight?
Dec
9
comment A “What's my vector?” game
Is there any strategy for Bob that would terminate in less than $n$ steps? Or maybe Bob does not know $n$ either?
Dec
9
comment Given a point and circle, what's the equation of the line that is tangent?
Don't understand. You are given some point $P=(p_x,p_y)$ and the circle $C$ with equation $(x-h)^2 + (y-k)^2 = r^2$ for fixed $p_x, p_y, h, k, r$ and you are asking to find the equation of the line through $P$ tangent to $C$? But there are 2 such lines, which one are you looking for?
Dec
9
comment Derving the formula of a summation
Not sure what you are asking. What do you mean you were given a solution with $k^3 + (k-1)^3$ as a first step? Could you typeset the entire solution you were given?
Dec
9
comment linear transformation properties
@user108297 Use the standard $\delta-\epsilon$ definition of continuity from here, for example: en.wikipedia.org/wiki/… and plug in the above definition of $|T(\vec{x})| = |\vec{x}|$.
Dec
6
comment linear transformation properties
@user108297 yes - just compute both sides term by term. I forgot one thing - $|z| = \sqrt{z^T z}$. Made the changes...
Dec
5
comment linear transformation properties
@user108297 see the edit with a further hint
Dec
5
comment The set of all things. A thing itself?
Hi, Questboy, welcome to Math.SE
Nov
26
comment Deriving the PDF of extreme variables
@MathStudent The question does NOT ask for pdf of $X$, which we called $f_X(x)$. It asks for pdf of $Y$, which we called $f_Y(y)$, which I showed you how to derive in my answer.
Nov
26
comment Deriving the PDF of extreme variables
@MathStudent Your question implies CDF is given to you.
Nov
26
comment Deriving the PDF of extreme variables
@MathStudent no!!! $f_X(x)$ and $f_Y(x)$ are different functions! But you get it a similar way - pdf is the derivative of the cdf, so $f_X(x) = F'_X(x)$.
Nov
26
comment Deriving the PDF of extreme variables
@MathStudent Yes, $f_X(x) = F_X'(x)$.
Nov
25
comment Find an eigevector corresponding to each eigenvalue of the matrix (4,1)(2,3). Is this matrix diagonalisable?
en.wikipedia.org/wiki/Matrix_diagonalization#Diagonalization
Nov
25
comment Deriving the PDF of extreme variables
@MathStudent The argument for $F_Y(y)$ in terms of $F_X$ is only possible if they evaluate the same thing :) otherwise how can you draw any conclusions? What you are really saying is $$ F_Y(y) = \mathbb{P}[Y \leq y] = \mathbb{P}[\max_{i=1}^n X_i \leq y] = \prod_{k=1}^n \mathbb{P}[X_i \leq y] = \prod_{k=1}^n F_X^n(y) = F_X^n(y). $$
Nov
25
comment Deriving the PDF of extreme variables
@MathStudent You had it wrong. I fixed your question also. Otherwise the equation makes no sense - LHS in $y$ and RHS in $x$, but also the proof makes no sense either...