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Long's user avatar
Long
  • Member for 8 years, 3 months
  • Last seen more than a week ago
  • University of EST of CHINA(UESTC)
5 votes
1 answer
279 views

Given $\int_0^{\infty}e^{-x^2}dx = \frac{\sqrt{\pi}}{2}$, evaluate $\int_0^{\infty}e^{-a^2x^2-\frac{b^2}{x^2}}dx $

2 votes
0 answers
37 views

coordinate transformation from $S = \{(u,v)\}\big|0\leq u,v \leq 1\}$ to $D = \{(x,y)\big| 0\leq y\leq2;|x|\leq \frac{y^2}{4}-1 \}$

2 votes
2 answers
743 views

Why does this optimization problem have a closed form solution that resembles least squares so much?

2 votes
1 answer
74 views

given $f(x)$ is continuous and $\int_0^{x^2}f(t)dt = x+sin\frac{\pi}{2}x$,solve $f(1)=?$

1 vote
1 answer
2k views

why the vector derivative of $\frac{d(x^Ta)}{dx} = \frac{d(a^Tx)}{dx} = a^T$, why it's $a^T$ not $a$

1 vote
1 answer
933 views

how to understand the conditional probability point of view of linear regression?

1 vote
1 answer
2k views

gradient of trace$(ABA^TC)$ w.r.t a Matrix A.

0 votes
3 answers
2k views

If $\omega = e^{(\frac{2\pi i}{n})}$ why $1+ \omega + \omega^{2} + ... + \omega^{n-1} = 0 $? [duplicate]

0 votes
3 answers
100 views

Is it OK to cancel absolute value $|x|$ in such a integral $\int_{-\infty}^0\frac{1}{{|x|}^p}dx$ using $|x| = (-x)$?