Pink Because of this, the pink triangle has become a symbol of the modern gay rights movement. The transition to pink as a sexually differentiating color for girls occurred gradually, through the selective process of the marketplace, in the 1930s and 40s. In the 1920s, some groups had been describing pink as a masculine color, an equivalent of the red that was considered to be for men, but lighter for boys. But stores nonetheless found that people were increasingly choosing to buy pink for girls, and blue for boys, until this became an accepted norm in the 1940s. In optics, the
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