Pink triangle and the LGBT rights movement. In Nazi concentration camps, each prisoner was required to wear a downward-pointing, equilateral triangular cloth badge on their chest, the color of which identified the reason for their imprisonment. Early on, homosexual male prisoners were variously identified with a green triangle (indicating criminals) or red triangle (political prisoners), the number "175" (referring to Paragraph 175, the section of the German penal code criminalizing homosexual activity), or the letter "A" (which stood for "Arschficker", literally "ass fucker"). Later, the use of a pink triangle was established for prisoners identified as homosexual men, which also included bisexual
Reuleaux triangle a figure of three overlapping semicircles (each two of which form a vesica piscis symbol) that again has a Reuleaux triangle at its center; just as the three circles of the Venn diagram may be interlaced to form the Borromean rings, the three circular arcs of the triquetra may be interlaced to form a trefoil knot. Relatives of the Reuleaux triangle arise in the problem of finding the minimum perimeter shape that encloses a fixed amount of area and includes three specified points in the plane. For a wide range of choices of the area parameter, the optimal solution to