Showing what's behind the curtain

Find how many Pythagorean triangles allow tiling with a perimeter < 100,000,000.

Investigating isosceles triangle for which the height and base length differ by one.

Investigate the Diophantine equation *x*^{2} − D*y*^{2} = 1.

Finding the number of blue discs for which there is 50% chance of taking two blue.