Tin foil hat "Signs" and "". Tin foil hat A tin foil hat is a hat made from one or more sheets of aluminium foil, or a piece of conventional headgear lined with foil, worn in the belief or hope that it shields the brain from threats such as electromagnetic fields, mind control, and mind reading. The notion of wearing homemade headgear for such protection has become a popular stereotype and byword for paranoia, persecutory delusions, and belief in pseudoscience and conspiracy theories. Note that "tin foil" is a common misnomer for aluminium foil; packaging metal foil was formerly made out of tin
FOIL method FOIL method In elementary algebra, FOIL is a mnemonic for the standard method of multiplying two binomials—hence the method may be referred to as the FOIL method. The word "FOIL" is an acronym for the four terms of the product: The general form is: Note that is both a "first" term and an "outer" term; is both a "last" and "inner" term, and so forth. The order of the four terms in the sum is not important, and need not match the order of the letters in the word FOIL. The FOIL method is a special case of a more