Maths AA terms: N

N

Natural domainalso largest possible domain

The largest set of real numbers for which a formula gives a real output: values that would mean dividing by zero, taking the square root of a negative number or the logarithm of a non-positive number are left out.

Introduced in 2.2 Functions, domain, range and inverse

Natural logarithmalso ln

A logarithm with base $e$, written $\ln x$. So $\ln x = y$ exactly when $e^y = x$, for $x > 0$.

Introduced in 1.5 Exponents and introduction to logarithms

Net (of a solid)

A flat shape that folds up to make the surface of a solid. The area of the net equals the surface area of the solid.

Introduced in 3.1 Distance, midpoint, volume and surface area

Newton's law of coolingHL only

The model in which an object's temperature $T$ changes at a rate proportional to the difference between $T$ and the surrounding temperature $T_s$: $\frac{dT}{dt} = -k(T - T_s)$

Normal (to a curve)also normal line

The straight line through a point on a curve that is perpendicular to the tangent at that point. If the tangent has gradient $m \neq 0$, the normal has gradient $-\frac{1}{m}$.

Introduced in 5.4 Tangents and normals

Normal distributionalso bell curve, N(μ, σ²)

A continuous probability distribution with a symmetric, bell-shaped curve, fixed by its mean $\mu$ and variance $\sigma^2$ and written $X \sim N(\mu, \sigma^2)$

Normal vectorHL only · also normal to a plane

A non-zero vector perpendicular to a plane, and so perpendicular to every line lying in that plane.

Introduced in 3.17 Vector equations of planes

nth rootalso cube root, square root

A number which, raised to the power $n$, gives $a$; written $\sqrt[n]{a} = a^{1/n}$

nth roots (of a complex number)HL only · also complex roots

The $n$ distinct solutions of $z^n = w$ for a non-zero complex number $w$. They have equal modulus $|w|^{1/n}$

Numerical solutionalso approximate solution

A solution found approximately, for example from a graph or by a GDC, given as a decimal to a stated accuracy. It is used when no algebraic method can isolate the variable.

Introduced in 2.10 Solving equations