# Puzzles

## Archive

Show me a random puzzle**Most recent collections**

#### Sunday Afternoon Maths LXVII

Coloured weightsNot Roman numerals

#### Advent calendar 2018

#### Sunday Afternoon Maths LXVI

Cryptic crossnumber #2#### Sunday Afternoon Maths LXV

Cryptic crossnumber #1Breaking Chocolate

Square and cube endings

List of all puzzles

## Tags

taxicab geometry bases symmetry polygons functions calculus geometry sum to infinity numbers averages chess volume graphs time perfect numbers circles means regular shapes surds multiplication unit fractions wordplay square roots quadratics perimeter square numbers irreducible numbers planes odd numbers multiples books balancing factorials cryptic clues mean rectangles scales dates cryptic crossnumbers sport percentages differentiation probabilty people maths dodecagons folding tube maps dice shapes trigonometry fractions clocks integration crossnumbers coordinates parabolas christmas speed chocolate digits partitions complex numbers triangles palindromes division crosswords rugby 3d shapes games squares pascal's triangle floors remainders 2d shapes prime numbers doubling angles triangle numbers routes ave ellipses shape hexagons area coins integers colouring menace number star numbers advent sums chalkdust crossnumber logic spheres lines cards grids sequences addition indices algebra probability arrows proportion factors money cube numbers## Complex squares

For which complex numbers, \(z\), are \(\mathrm{Re}(z^2)\) and \(\mathrm{Im}(z^2)\) both positive?