Henny Joyce Lim, a flight attendant for Philippines-based airline Cebu Pacific, is sharing the "secret" meaning behind black triangle stickers in airplane cabins. eric1207cvb - stock.adobe.com ...

A 2018 study found that the likelihood of adults with braces developing black triangles between their upper and lower incisor teeth was 22 percent and 36 percent, respectively.

This is a simple story, but it takes a little while to think about. Look at repeating black triangles (imagine they continue infinitely). The area of the ALL black triangles takes up 1/3 the area of ...