Reputation
3,229
Top tag
Next privilege 5,000 Rep.
Approve tag wiki edits
Badges
9 30
Newest
 Nice Answer
Impact
~108k people reached

Aug
27
comment Evaluating This Complex Line integral
Yes. But as you say it's rather ugly ! See Jack's answer below...
Aug
27
comment Evaluating This Complex Line integral
You could try letting $z=\sin(t^2)-i\frac{2t^2}{\pi}$ and substitute into the integral. Use the limits $0$ and $\sqrt{\pi/2}$. But maybe you tried that already.
Aug
26
comment Abuse of notation ? $(A\mid M_{n\times p})$ to denote a set of matrices…
@A.G. Good point !
Aug
26
revised Abuse of notation ? $(A\mid M_{n\times p})$ to denote a set of matrices…
edited title
Aug
26
comment Abuse of notation ? $(A\mid M_{n\times p})$ to denote a set of matrices…
A matrix in $M_{n\times (m+q)}$ where $q $ is the number of columns of $B $, so long as $B $ has $n $ rows. At least that's what I'd want it to be...
Aug
26
revised Abuse of notation ? $(A\mid M_{n\times p})$ to denote a set of matrices…
added 6 characters in body
Aug
26
comment Abuse of notation ? $(A\mid M_{n\times p})$ to denote a set of matrices…
Ah yes i see as they're both sets of matrices.
Aug
26
revised Abuse of notation ? $(A\mid M_{n\times p})$ to denote a set of matrices…
deleted 39 characters in body
Aug
26
asked Abuse of notation ? $(A\mid M_{n\times p})$ to denote a set of matrices…
Aug
26
revised Is this “truncating” matrix function well known?
deleted 3 characters in body
Aug
26
comment Is this “truncating” matrix function well known?
Ok, thanks all. I think I'll stick with my $\tau$ definition. As A.G. says, submatrix is good, but my submatrix is very special so the usual notation may be overkill. I don't think $A_r$ would be great because my matrices can be made up many multiplications, so it may be confusing. I like the idea of projection, but projections have a huge theory surrounding them and I don't intend to use that where $\tau$ is concerned. I may be using projections later on, so this might also cause confusion if mixing notation. Interesting to be reminded of submatrices and projections in this context though !
Aug
26
comment Is this “truncating” matrix function well known?
Maybe my original definition in the question is fine then?
Aug
26
comment Is this “truncating” matrix function well known?
Good point ! Thanks. I think using $\pi_r$ would be more natural.
Aug
26
comment Is this “truncating” matrix function well known?
So maybe I could say "... define the projection $\pi_r:M_{n\times n}\to M_{n\times r}$ where $r\leq n$..." without having to mention how the function is defined due to the presence of the word "projection" in the definition statement.
Aug
26
asked Is this “truncating” matrix function well known?
Aug
23
comment Need help with slope of a line problems
You should spend some time breaking the question down. Chop the question up into identifiable chunks which you understand the meaning of on their own. Write these down if need be. Then figure out what the question is asking as a whole from there. This is a skill you'll need for lots of subjects in future.
Aug
20
comment find smallest $x>0$ such that $\frac{A}{cx}e^{-cx^2}\le \varepsilon$
Just a thought... if $0<x<1$ you may be able to expand $Ae^{-cx^2}\leq cx\varepsilon,$ and use $-Acx^2-cx\varepsilon\leq O(x^4)$...
Aug
20
revised Prove a function containing integrals is positive
edited body
Aug
20
comment Is there a name for a general upper triangular hollow matrix?
Hi Ofir, do you know if such matrices are denoted in a special way, e.g. an upper triangular matrix might be denoted $U$, whereas a strictly upper triangular matrix could be $U^*$, for example. Is there a standard notation or not?
Aug
20
accepted Is there a name for a general upper triangular hollow matrix?