N2 numbers are arranged in a square pattern. Select one of the numbers and try answering computer queries. After two attempts, computer will reveal your selected number.
http://www.cut-the-knot.org/Curriculum/Magic/MagicInSquare.shtml
The applet consists of two 3x3 arrays. On the left, the small one shows the target configuration. To modify the target configuration, click on the squares you want modified.
http://www.cut-the-knot.org/Curriculum/Algebra/Merlin.shtml
In this simple game, your computer does all the work. You only have to press one of the buttons, "Yes" or "No".
http://www.cut-the-knot.org/blue/Cards.shtml
Poles and polars come in pairs. Poles are plane points; polars are straight lines in the same plane.
http://www.cut-the-knot.org/Curriculum/Geometry/PolePolar.shtml
At the beginning, the applet displays 2N natural numbers: 1, 2, 3, ..., 2N - 1, 2N. Select any N numbers by clicking on N numbers in turn.
http://www.cut-the-knot.org/Curriculum/Games/ProizvolovGame.shtml
Let's build up squares on the sides of a right triangle.
http://www.cut-the-knot.org/pythagoras/index.shtml
hen the dot on the line is not confined to the grid, the dot appears to move freely. However, its center's location is naturally restricted to the pixels of your screen
http://www.cut-the-knot.org/Curriculum/Algebra/PythagoreanTriples.shtml
Self-documenting sentences of the sort offered by the applet below, have been invented by Raphael Robinson [Hofstadter, p 27 and p 389 and on; see also Gale, p 10].
http://www.cut-the-knot.org/Curriculum/Algebra/SelfDescriptive.shtml
In a triangle, an altitude is a segment of the line through a vertex perpendicular to the opposite side. An altitude is the portion of the line between the vertex and the foot of the perpendicular.
http://www.cut-the-knot.org/triangle/altitudes.shtml
For every angle, there exists a line that divides the angle into two equal parts. This line is known as the angle bisector. In a triangle, there are three such lines.
http://www.cut-the-knot.org/triangle/ABisector.shtml