Hvad er vinkelsummen for en trekant tegnet på en kugle ?
/Sik
What is the total degree sum of the angles in a triangle drawn on a sphere?
/Sik
Quote
From Amanda Briney
A great circle is defined as any circle drawn on a globe (or other sphere) with a center that includes the center of the globe. Thus, a great circle divides the globe into two equal halves. Since they must follow the circumference of the Earth to divide it, great circles are about 40,000 kilometers (24,854 miles) in length along meridians. At the equatorthough, a great circle is a little bit longer as the Earth is not a perfect sphere. [...]
Appearance on Maps
To determine great circle routes for navigation or other knowledge, the gnomic map projection is often used. This is the projection of choice because on these maps the arc of a great circle is depicted as a straight line. These straight lines are then often plotted on a map with the Mercator projection for use in navigation because it follows true compass directions and is therefore useful in such a setting.
Read more: http://geography.about.com/od/understandmaps/a/greatcircle.htm
It is important to note though that when long distance routes following great circles are drawn on Mercator maps, they look curved and longer than straight lines along the same routes. In reality though, the longer looking, curved line is actually shorter because it is on the great circle route. [...]
Read more: http://geography.about.com/od/understandmaps/a/greatcircle.htm
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