MathDB

2

Part of 2003 Pan African

Problems(2)

Circumference

Source: Pan African 2003

10/4/2005
The circumference of a circle is arbitrarily divided into four arcs. The midpoints of the arcs are connected by segments. Show that two of these segments are perpendicular.
divisible by 21

Source: Pan African 2003

10/4/2005
Find all positive integers nn such that 2121 divides 22n+2n+12^{2^n}+2^n+1.