problem
Favourite
Circles ad infinitum
A circle is inscribed in an equilateral triangle. Smaller circles
touch it and the sides of the triangle, the process continuing
indefinitely. What is the sum of the areas of all the circles?
problem
Favourite
Direct logic
Can you work through these direct proofs, using our interactive proof sorters?
problem
AP train
An arithmetic progression is shifted and shortened, but its sum remains the same...
problem
Speedy summations
Watch the video to see how to add together an arithmetic sequence of numbers efficiently.