Skip to main content
Amir reza Riahi's user avatar
Amir reza Riahi's user avatar
Amir reza Riahi's user avatar
Amir reza Riahi
  • Member for 4 years, 6 months
  • Last seen this week
3 votes
2 answers
415 views

Why do both $\iint_R(x^2+y^2)\ dA$ and $\iiint_E 1\ dxdydz$ give the volume of $z=x^2+y^2$? What is the difference between $R$ and $E$?

3 votes
1 answer
425 views

How many matrices in which product of numbers in each row and column is 1?

2 votes
1 answer
244 views

singular values of $A-\alpha I_n$ while $A\in\mathbb{C}^{n\times n}$

2 votes
1 answer
95 views

What is meaning of $X/P$? ($X$ is a set and $P$ is a partition)

2 votes
3 answers
99 views

How to evaluate $\iint_R \sin(\frac{y-x}{y+x})dydx$ with Jacobian substitution?

1 vote
1 answer
104 views

How to prove $a^x\times a^y=a^{x+y}$ for cardinals? [duplicate]

1 vote
1 answer
88 views

why $\sin t^2$ can't be an answer of equation $y'' + p(t)y'+q(t)y=0$?

1 vote
1 answer
2k views

Why natural numbers don't have supremum?

0 votes
1 answer
287 views

How to solve this improper integral using Simpson's rule [closed]

0 votes
1 answer
130 views

Show that $(A-I)^{-1}(A+I)$ is orthogonal if $A$ is skew-symmetric

0 votes
1 answer
67 views

How to calculate limit of a recursive without starting point? [duplicate]

0 votes
2 answers
102 views

How do we define power of irrational numbers?

0 votes
1 answer
179 views

What is the connection between vector functions and space curves?

0 votes
1 answer
128 views

How to prove $\sum_{i=1}^n i.i! = (n+1)!-1$ with mathematical induction? [duplicate]

0 votes
1 answer
106 views

How to prove $\int_0^\infty\int_0^\infty e^{-x^2 -y^2}dxdy= (\int_0^\infty e^{-x^2}dx)(\int_0^\infty e^{-y^2}dy)$?