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user217285
  • Member for 9 years, 3 months
  • Last seen more than a month ago
66 votes
Accepted

Why is the matrix product of 2 orthogonal matrices also an orthogonal matrix?

17 votes

Why do calculus students learn to think of the derivative as a limit?

17 votes

Why the determinant of a matrix with the sum of each row's elements equal 0 is 0?

12 votes
Accepted

Why is $f(x) = x^2$ uniformly continuous on [0,1] but not $\mathbb{R}$

11 votes
Accepted

Continuity Must Hold in an Entire Open Set?

10 votes
Accepted

Impossible numbers drawn from tricky function

9 votes

Prove $||Px|| = ||x||$ for Orthogonal Matrices

8 votes
Accepted

Show that there exist unbounded sequences, $x_n\neq y_n$, such that $x_n-y_n\rightarrow 0$ as $n\rightarrow \infty$

8 votes

Find the limit $\lim_{n \to \infty} \sum_{k=1}^n \frac{1}{k+n}$

8 votes
Accepted

Evaluating a limit?

7 votes
Accepted

Sum of non-real roots of equation?

7 votes
Accepted

If $f$ is a bounded function on an interval E, and E has measure $0$ , Is $f$ measurable? What is the value of it's $\int_E f$?

6 votes

The function $f$ is Riemann integrable on $[-1,1]$. For any interval in $[-1,1]$, there are always both positive and negative values of $f(x)$.

6 votes
Accepted

Derivatives Must Exist over an Entire Open Set?

6 votes

Proving a trigonometric identity with tangents

6 votes

Find the value of $\frac{x}{y+z}+\frac{y}{z+x}+\frac{z}{x+y}$

6 votes

Linear Algebra Done Right Example 1.7

5 votes
Accepted

Looking for a function that fits a certain criteria

5 votes
Accepted

The spectral norm of a positive definite matrix is its largest eigenvalue

5 votes

Absolute value of definite integral: If $\big|\int^b_af(x) dx \big|\le(b-a)^2$ prove that $f(x)=0$ for all $x \in \mathbb{R}$.

5 votes

Collecting proofs for $\sum_{n=2}^{\infty} \, \frac{n-1}{2^n} = 1$

4 votes
Accepted

How to find a commuting element in group of permutaions

4 votes
Accepted

Explain (without calculating the eigenvalues and eigenvectors) why the following matrix is NOT diagonalizable:

4 votes
Accepted

Distinct eigenvalues and matrices problem

4 votes
Accepted

Intuitive explanation of binomial coefficient formula

4 votes
Accepted

Limit of $\frac{n^n}{(n+1)^n}$ as n approaches infinity

4 votes

Discontinuous function with continuous derivative

4 votes
Accepted

How to show the average x-coordinates of four collinear points on the curve is a constant?

4 votes

If $\alpha, \beta, \gamma$ solutions for the equation

4 votes
Accepted

Why does a vector space over $\mathbb{C}$, $\mathbb{R}$, or $\mathbb{Q}$ have either 1 element or infinitely many elements?

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