Rodrigo de Azevedo

 73 Is “The empty set is a subset of any set” a convention? 72 Why are some coins Reuleaux triangles? 40 The relation between trace and determinant of a matrix 30 How to prove that a $3 \times 3$ Magic Square must have $5$ in its middle cell? 28 What is a real-world metaphor for irrational numbers?

### Reputation (13,396)

 +10 Minimize $\mbox{trace}(AX)$ over $X$ with a positive semidefinite $X$ +20 How to prove that a $3 \times 3$ Magic Square must have $5$ in its middle cell? +10 Solve $\frac{1}{x} = S x$, an equation that includes an element-wise inverse +10 How can the infinity norm minimization problem be rewritten as a linear program?

### Questions (8)

 13 What is the volume of the $3$-dimensional elliptope? 5 Writing a convex quadratic program (QP) as a semidefinite program (SDP) 4 Prove that $\nabla_{\mathrm X} \mbox{tr} (\mathrm A \mathrm X^{-1} \mathrm B) = - \mathrm X^{-\top} \mathrm A^\top \mathrm B^\top \mathrm X^{-\top}$ 3 Maximize $\langle \mathrm A , \mathrm X \rangle$ subject to $\| \mathrm X \|_2 \leq 1$ 3 What theorem in topology was Claude Shannon referring to?

### Tags (304)

 492 matrices × 260 99 derivatives × 62 388 linear-algebra × 218 86 convex-optimization × 65 206 optimization × 163 84 systems-of-equations × 46 107 determinant × 44 82 geometry × 10 102 matrix-calculus × 68 78 logic × 6

### Accounts (57)

 Mathematics 13,396 rep 42065 MathOverflow 1,862 rep 2922 Chemistry 920 rep 817 Aviation 826 rep 1519 Stack Overflow 782 rep 617