Area air defence, the air defence of a specific area or location, (as opposed to point defence), have historically been operated by both armies (Anti-Aircraft Command in the British Army, for instance) and Air Forces (the United States Air Force's CIM-10 Bomarc). Area defence systems have medium to long range and can be made up of various other systems and networked into an area defence system (in which case it may be made up of several short range systems combined to effectively cover an area). An example of area defence is the defence of Saudi Arabia and Israel by MIM-104 Patriot missile batteries during the first Gulf War, where the objective was to cover populated areas.
What is the air defence of a certain area called?
Area air defence

The sector, a calculating instrument used for solving problems in proportion, trigonometry, multiplication and division, and for various functions, such as squares and cube roots, was developed in the late 16th century and found application in gunnery, surveying and navigation.
The sector, a calculating instrument, was invented during what century?
16th century

In 1995, Oklahoma City was the site of one of the most destructive acts of domestic terrorism in American history. The Oklahoma City bombing of April 19, 1995, in which Timothy McVeigh and Terry Nichols detonated an explosive outside of the Alfred P. Murrah Federal Building, killed 168 people, including 19 children. The two men were convicted of the bombing: McVeigh was sentenced to death and executed by the federal government on June 11, 2001; his partner Nichols is serving a sentence of life in prison without the possibility of parole. McVeigh's army buddy, Michael Fortier, was sentenced to 12 years in federal prison and ordered to pay a $75,000 fine for his role in the bombing plot (i.e. assisting in the sale of guns to raise funds for the bombing, and examining the Murrah Federal building as a possible target before the terrorist attack). His wife, Lori Fortier, who has since died, was granted immunity from prosecution in return for her testimony in the case.
Who committed the Oklahoma City Bombing?
Timothy McVeigh and Terry Nichols