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DescriptionSurfacesWithAndWithoutBoundary.svg
Some surfaces without boundary (left) and with boundary (right). (Also called closed surfaces and open surfaces, respectively.) Left: Surface of a sphere, surface of a torus, surface of a cube. Right: Disk surface, square surface, surface of a hemisphere. The surface is blue, the boundary is red.
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{{Information |Description=Some surfaces without boundary (left) and with boundary (right). (Also called closed surfaces and open surfaces, respectively.) Left: Surface of a sphere, surface of a torus, surface of a cube. Right: Disk surface, square surfac