No matter how you choose to place the red points on the circumference, the three blue points will lie on a straight line (shown in red). This works for any conic (which may be a circle, ellipse, parabola or hyperbola).
Math Humor
Mathematics is sometimes weird… Read more: The hole truth of topology.
“Stubborn” Number 33
It is conjectured that n is a sum of 3 cubes if n is a number that is not congruent to 4 or 5 mod 9. The number 33 enters this category, but for 64 years no solutions emerged — that is, whether the equation 33 = x³ + y³ + z³ has an integer solution. Continue reading ““Stubborn” Number 33″
Sangaku: Semicircle inscribed in a right triangle
Find the radius r of the semicircle inscribed in the right triangle below:
show solution
Cauchy Product
A clever visualization of a Cauchy Product.
Each black square has value 1, each red square has value -1.
Smallest Prime Number Magic Square
American mathematician Harry L. Nelson won the challenge to produce a 3 × 3 magic square containing the smallest consecutive primes:
Fibonacci Spiral Jigsaw Puzzle
Each piece of this puzzle is similar (the same shape at a different size). The placement of the pieces is based on the golden angle (≈137.5º), and results in a pattern frequently found in nature (phyllotaxis), for instance on sunflowers. The puzzle features 8 spirals in one direction, and 13 in the other. You can build your own Fibonacci spiral puzzle by following John Edmark’s tutorial.
Circles and Golden Ratio
The last digit of the numbers in the Fibonacci Sequence are cyclic, they form a pattern that repeats after every 60th number: 0, 1, 1, 2, 3, 5, 8, 3, 1, 4, 5, 9, 4, 3, 7, 0, 7, 7, 4, 1, 5, 6, 1, 7, 8, 5, 3, 8, 1, 9, 0, 9, 9, 8, 7, 5, 2, 7, 9, 6, 5, 1, 6, 7, 3, 0, 3, 3, 6, 9, 5, 4, 9, 3, 2, 5, 7, 2, 9, 1.
Illusive Number
If you can see the 8 in the middle of the 8 of diamonds you are a visual thinker rather than a verbal thinker.
Math Ambigram
(by Peter Rowlett)
Solve this equation for x. Then rotate 180° and solve for x again.
The equation works either ways as 𝑥, 1, 8 and the unusual 5 have rotational symmetry. The same is true of +, =, and the horizontal line in a fraction.
