N

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Nabla Squared : The Laplacian written as V²

Nadir

The point on the celestial sphere in the direction downwards of the plumb-line. The Zenith , the observer and the nadir are always in a straight line.

Native set  theory : Set is defined as collection of objects or container of objects. In this sense, ‘set’ is an undefined concept. Similarly when we say an object ‘ belongs to’ or ‘ is a member of’ a set without rigorously defining what it means. This approach to set theory is called “ Native Set Theory” as opposite to “ Axiomatic Set Theory “.

Nano : Prefix having meaning 10^-9. E.g. 1 nanometer  = 10^-9 meter .

Napier, John : ( 1550-1667 ) : Philosopher and Mathematician inventor of logarithms and decimal point. His other mathematical contributions include a mnemonic for formulas used in solving spherical triangles and two formulas known as Napier’s  analogies.

Napierian logarithm : A logarithm to the base e ( 2.71828). for example,                         In 10 = log_e 10 = 2.30, also called natural logarithm.

Napier’s bones ( Rods) : are numbered rods used to perform multiplication or division. These can be assumed to be predecessor to slide rule. ( u can see TLM related to this on www.mathsworld.in maths tlm section )

Napier’s formulae : Suppose a spherical triangle having sides a . band c and angles opposite to these sides are α , β and γ respectively. We have the following relationships, called Napier’s formulae.

Sin (a-b)/2   =   tan (α-β)/2

Sin (a+b)/2       tan γ/2

cos (a-b)/2   =   tan (α+β)/2

cos (a+b)/2      tan γ/2

Sin (α-β)/2   =   tan (a-b)/2  

Sin (α+β)/2       cos c/2

Cos  (α-β)/2   =   tan (a+b)/2  

Cos  (α+β)/2       tan c/2

Napier’s rules of Circular parts : These are related to the right spherical triangle. Using Napier’s rule of circular parts, any quantity can be calculated if only two quantities are known.

Nappe : One of the two pieces of a double cone, that is, two cones placed such that their vertices touch each other .

Nagel point

In a triangle, the lines from the vertices to the points of contact of the opposite sides with the excircles to those sides meet in a point called the Nagel point.

Natural Base : The base in natural logarithm.

Natural cubic spline : Splines are smooth functions with which to fit data, and when used for interpolation, they don’t have the oscillatory behavior, that is the characteristic of high degree polynomial interpolation.

Natural logarithm : Same as Napier’s logarithm. Also known as hyperbolic logarithm , is the logarithm to the base e (2.71828).

Natural number

Numbers used for counting objects. Any one of the numbers 1, 2, 3, 4, 5, ... .zero ( 0)  is not included .

Nautical Mile : A nautical mile was developed to be a distance equal to one minute of arc ( 1/60 of a degree ) distance  along a great circle and is equal to 6076 feet.              1 knot = 1 nautical mile pe hour = 0.5144 m/sec.

Necker Cube : Wire frame drawing of a cube in isometric perspective , which means that the parallel edges of the cube are drawn as parallel lines in the picture.

Needle Problem : Also called Buffon’s needle problem. It involves dropping a needle on a lined sheet of paper and determining the probability of the needle crossing one of the lines on the page. The remarkable result is that the probability is directly related to the value of π.

Negative number

A number smaller than 0.    Number line  …….-5,-4,-3,-2, -1,0,1,2,3,4,5,…………..

Nine point center

In a triangle, the circumcenter of the medial triangle is called the nine point center.

Nine point circle

In a triangle, the circle that passes through the midpoints of the sides is called the nine point circle.

Nomograph

A graphical device used for computation which uses a straight edge and several scales of numbers.

Nonagonal number : A number of the form n(7n-5)/2.

Nonary : associated with 9

Normal : perpendicular

Null hypothesis

The null hypothesis is the hypothesis that is being tested in a hypothesis-testing situation.

Null set: the empty set

Number line : A line on which each point represents a real number.

Number sentence : An arrangement of numbers and symbols; for example, an addition sentence: 3 + 7 = 10; a subtraction sentence: 12 – 4 = 8; a multiplication sentence: 5 x 7 = 35; a division sentence: 48 ÷ 6 = 8

 Number theory : The study of integers.

Numeral : A symbol that stands for a number.

Numerator : In the fraction x/y, x is called the numerator and y is called the denominator.

Numerical analysis : The study of methods for approximation of solutions of various classes of mathematical problems including error analysis.