Picture of the month
![](http://upload.wikimedia.org/wikipedia/commons/thumb/9/97/Triangles_%28spherical_geometry%29.jpg/360px-Triangles_%28spherical_geometry%29.jpg)
Credit: Lars H. Rohwedder
Spherical geometry is the geometry of the two-dimensional surface of a sphere. It is an example of a non-Euclidean geometry. Two practical applications of the principles of spherical geometry are navigation and astronomy. On a sphere, the sum of the angles of a triangle is not equal to 180°.
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