This table: $$\begin{array}{|c|cc|} \hline +& 0& 1\\ \hline 0& 0& 1\\ 1& 1& 0\\ \hline \end{array}$$ "feels" right, but how can yo...

In High School Algebra , after studying how to plot a graph of $f(x)$ (rather called $y$) against $x$ in Cartesian coordinates, we studied several tests t...

Find all $2\times 2$ matrices that commute with $$\left( \begin{array}{cc} 2 & 3 \\ 1 & 4 \end{array} \right)$$ My progress: I know that a square ...

How many positive integers less than 10000 are there which contain a digit 2 or 3? Is this the right derivation? $$9\times9\times9\times8=5832$$ $$5832-2=...

Definition. Suppose that $\mathcal M$ is an $\mathcal L$-structure. Let $\mathcal L_M$ be the language where we add to $\mathcal L$ constant symbols $m$ f...

Is there a function to display large array on command prompt with displaying only part of it and waiting until user enters something from keyboard.

The following is a well-known result in functional analysis: If the vector space $X$ is finite dimensional, all norms are equivalent. Here is the standard...

I don't understand why it's apparently 'clear' that the matrix of $T$ with respect to the basis $v_1, \dots, v_n$ is a Jordan block of...

I'm in a quantum mechanics class, where people started using expressions such as: "operators $\hat{x}$ and $\hat{p}$ commute to $i\hbar$", to mean "$...

Given two wires each of diameter D and length L, what will be the new length after you twist the wires around each other 1 Turn? I mean that when you star...