Round-the-world journey
В благодарную память о uStas'е
http://tube.geogebra.org/ustas
Hot air balloon flying over Earth along a given parallel at a constant height,
was made round-the-world journey.
The difference between the distances travelled by the top and bottom points of the ball
was equal to twice the diameter of the ball.
At what latitude was made the journey?
Pull the green point to change a latitude.