QUES: Current circulating in one antenna generally induces a voltage across the feedpoint of nearby antennas or antenna elements. The mathematics presented below are useful in analyzing the electrical behaviour of antenna arrays, where the properties of the individual array elements (such as half wave dipoles) are already known. If those elements were widely separated and driven in a certain amplitude and phase, then each would act independently as that element is known to. However, because of the mutual interaction between their electric and magnetic fields due to proximity, the currents in each element are not simply a function of the applied voltage (according to its driving point impedance), but depend on the currents in the other nearby elements. Note that this now is a near field phenomenon which could not be properly accounted for using the Friis transmission equation for instance.

What are the mathmatic useful towards?
What is the answer?
ANS: electrical behaviour
QUES: In 2005, Argentina's indigenous population (known as pueblos originarios) numbered about 600,329 (1.6% of total population); this figure includes 457,363 people who self-identified as belonging to an indigenous ethnic group and 142,966 who identified themselves as first-generation descendants of an indigenous people. The ten most populous indigenous peoples are the Mapuche (113,680 people), the Kolla (70,505), the Toba (69,452), the Guarani (68,454), the Wichi (40,036), the Diaguita-Calchaqui (31,753), the Mocovi (15,837), the Huarpe (14,633), the Comechingon (10,863) and the Tehuelche (10,590). Minor but important peoples are the Quechua (6,739), the Charrua (4,511), the Pilaga (4,465), the Chane (4,376), and the Chorote (2,613). The Selknam (Ona) people are now virtually extinct in its pure form. The languages of the Diaguita, Tehuelche, and Selknam nations have become extinct or virtually extinct: the Cacan language (spoken by Diaguitas) in the 18th century and the Selknam language in the 20th century; one Tehuelche language (Southern Tehuelche) is still spoken by a handful of elderly people.

Who still speaks Southern Tehuelche?
What is the answer?
ANS: a handful of elderly people
QUES: Manhattan's skyline, with its many skyscrapers, is universally recognized, and the city has been home to several of the tallest buildings in the world. As of 2011, New York City had 5,937 high-rise buildings, of which 550 completed structures were at least 330 feet (100 m) high, both second in the world after Hong Kong, with over 50 completed skyscrapers taller than 656 feet (200 m). These include the Woolworth Building (1913), an early gothic revival skyscraper built with massively scaled gothic detailing.

How many buildings located in NYC are at least 330 feet in height?
What is the answer?
ANS:
550