A polyhedron (plural polyhedra or polyhedrons) is often defined as a geometric object with flat faces and straight edges (the word polyhedron comes from the Classical Greek ÏÎ¿Î»ÏÎµÎ´ÏÎ¿Î½, from poly- , stem of ÏÎ¿Î»ÏÏ, many, + -edron, form of ÎµÎ´ÏÎ¿Î½, base, seat, or face). polyhedron is any three-dimensional figure with flat surfaces that are polygons. Specifically, any geometric shape existing in three-dimensions and having flat faces, each existing in two-dimensions, which intersect at straight, linear edges.
In 1839, Charles Goodyear invented rubber vulcanization, but the first rubber condom was not produced until 1855. Just a few short years later, the majority of rubber companies were producing condoms as well. These condoms were reusable, which meant they were much more affordable.
I vaguely remember seeing the occasional mosquito coil when I was growing up in the United States but most people used bug spray and citronella candles. Mosquito coils were actually invented in Japan, at the end of the 19th century.A man named Ueyama Eiichiro was in the business of exporting mandarin oranges when Fukuzawa Yukichi, the famous author, statesman and founder of Keio University, introduced him to a seed trader in the United States. vaguely remember seeing the occasional mosquito coil when I was growing up in the United States but most people used bug spray and citronella candles. Mosquito coils were actually invented in Japan, at the end of the 19th century.