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Vesica piscis
Shape that is the intersection of two circles with the same radius / From Wikipedia, the free encyclopedia
The vesica piscis is a type of lens, a mathematical shape formed by the intersection of two disks with the same radius, intersecting in such a way that the center of each disk lies on the perimeter of the other.[1] In Latin, "vesica piscis" literally means "bladder of a fish", reflecting the shape's resemblance to the conjoined dual air bladders (swim bladder) found in most fish.[2] In Italian, the shape's name is mandorla ("almond").[3] A similar shape in three dimensions is the lemon.
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This figure appears in the first proposition of Euclid's Elements, where it forms the first step in constructing an equilateral triangle using a compass and straightedge. The triangle has as its vertices the two disk centers and one of the two sharp corners of the vesica piscis.[4]