﻿ ﻿﻿﻿ 以 e 开头的数学词汇 | 玄数
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## 以 e 开头的数学词汇

2012-10-07
(Euler’s Number)   欧拉常数

### γ ≈ 0.57721566490153286060

eccentricity   离心率
Denoted e or ε, is a parameter associated with every conic section. It can be thought of as a measure of how much the conic section deviates from being circular.

### (1 – e2) x2 + y2 – 2pe2x – p2e2 = 0

edge   边缘
The outside limit of an object, a surface or an area; The part furthest from the centre.

element   元素

• a. A member of a set.
• b. A point, line, or plane. A part of a geometric configuration, such as an angle in a triangle.
• c. The generatrix of a geometric figure.
• d. Any of the terms in the rectangular array of terms that constitute a matrix or determinant.

ellipse   椭圆
A closed, symmetric curve shaped like an oval, which can be formed by intersecting a cone with a plane that is not parallel or perpendicular to the cone’s base. The sum of the distances of any point on an ellipse from two fixed points (called the foci) remains constant no matter where the point is on the curve.

engineering notation   工程计数法
A version of scientific notation in which the exponent of ten must be divisible by three. As an alternative to writing powers of 10, SI prefixes can be used, which also usually provide steps of a factor of a thousand.On calculators, engineering notation is named “ENG”.

enlarge   扩大
To increase the size, amount, or extent of something, or become larger.

equal   等于, 相等的
Being the same or identical to in size, quantity, value, or standard.

equal sign   等号
symbol: =

equality   相等
A statement that two quantities are equal; equation.

equation   方程
A mathematical statement that two expressions, usually divided by an equal sign, are of the same value.

equation of a straight line   直线的方程

equiangular triangle / equilateral triangle   等边三角形
A triangle which three sides and angels are both equal.

equidistant   等距离
Equally distant.

equinox   春分、秋分; 二分点

• Either of the two times during a year when the sun crosses the celestial equator and when the length of day and night are approximately equal, occurring about March 21 (vernal equinox or spring equinox) and September 22 (autumnal equinox).
• Either of two points on the celestial sphere at which the ecliptic intersects the celestial equator.

equivalent   相等，等价物

• Being the same, or effectively the same, in effect, value, or meaning as something and usually interchangeable with it.
• Describes geometric figures that have different shapes but equal areas.
• Having the same set of solutions: describes equations that share a common solution or solutions, e.g. for both 2x-3 = x+2 and x-5 = 0 the solution is x = 5.

estimate   估量；计量
To form an approximate judgment or opinion regarding the worth, amount, size, weight, etc.

evaluate   估价；计算

• To judge or determine the significance, worth, or quality of.
• To calculate a numerical value for a mathematical expression.

even number   偶数
A number that can be exactly divided by 2, such as 2, 4, 6, 8, etc.

expanded notation   扩展计数法
The representation of a number as the sum of a series of terms, each of which is written explicitly as the product of a digit and the base of the number system raised to some power.

exponent   指数, 幂
A raised figure or symbol that shows how many times a quantity must be multiplied by itself, it’s a symbol or number placed above and after another symbol or number to denote the power. In the expressions x2 and xn, the number 2 and the letter n are the exponents respectively of the base x.

exponential function   指数函数
The function of the form like: y = ax.

expression   表达式
A variable, function, or some combination of constants, variables, or functions.

exterior angle   外角内; 对角

• An angle formed outside a polygon by one side and an extension of an adjacent side; the supplement of an interior angle of the polygon.
• An angle formed outside parallel lines by a third line that intersects them.

extraneous root   增根
A root that is introduced into an equation in the process of solving another equation, but is not a solution of the equation to be solved. For example: the equation log2 (x – 5) + log2 (x – 3) = 3 has the single root x = 7. If, however, we take antilogarithms, we obtain the equation (x – 5)(x – 3) = 8. It has not only the root x = 7 but also the root x= 1, which is an extraneous root of the initial equation.

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