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
9-j symbol diagonal as well as even permutations of its rows or columns: An odd permutation of rows or columns yields a phase factor formula_27, where For example: The 9-"j" symbols can be calculated as sums over triple-products of 6-"j" symbols where the summation extends over all admitted by the triangle conditions in the factors: When formula_31 the 9-"j" symbol is proportional to a 6-j symbol: The 9-"j" symbols satisfy this orthogonality relation: The "triangular delta" is equal to 1 when the triad ("j", "j", "j") satisfies the triangle conditions, and zero otherwise. The 6-j symbol is the first representative, , of