Online Math Dictionary: E

Easy to understand math definitions for K-Algebra mathematics
Just scroll down or click on the word you want and I'll scroll down for you!

edge ellipse ellipsoid
empty set equality equation
equidistant equilateral triangle estimate
even number expanded notation exponent
exponential exterior angle  


The edges of a polygon are the outside boundaries.  In thesquare on the right, you can see four  edges.   In a polyhedron, like the dodecahedron on the right, an edge is where two faces meet.  The edges are the yellow lines

edges of a square and dodecahedron

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There's an easy definition for an ellipse and a harder algebra definition.  Here's the easy one:   An ellipse is a stretched out circle.
For the algebra definition, check out.Coolmath Algebra Ellipses

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An ellipsoid is a three dimensional ellipse.  Imagine putting a line through the longest part of an ellipse and spinning it.  This would give you an ellipsoid.


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Empty Set
An empty set is the same as a "null set."  An empty set is a set with no members (or elements.)  The symbol for the empty set is on the right.  It can also be written as an empty set of set brackets:  
                                      {   }
Putting the empty set symbol inside the set brackets is a bad thing...  But, is a common mistake, so don't do it!

empty set symbol


A math statement showing that two things are equal.
Example:   3 + 2 = 5

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A math statement showing that two things are equal.  (Same thing as an equality.)
Example:   3 + 2 = 5

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Equidistant just means "the same distance."

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Equilateral Triangle
An equilateral triangle is a triangle whose sides are all the same length (congruent).

For more info, check out Properties of TrianglesTriangle Notations and Types of Triangles

equilateral triangle

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When you estimate the answer to a problem it means that you give a pretty good guess at what the answer will be.
Example:   199 x 302 =      Well, that's close to 200 x 300 which is 60,000. (I can do that in my head).   So, my estimate for the answer is 60,000.  The real answer is 60,098.

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Even Number
An even number is a number that is cleanly divisible by 2.  (When I say "cleanly divisible" I mean that there is noremainder.)
Example:  2, 4, 6, 8, ...

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Expanded Notation
Expanded notation is when you write a number out to show all the place values.
Example:   5682 = ( 5 x 1000 ) + ( 6 100 ) + ( 8 10 )  + ( 2 1 )
For more info, check out my decimals lesson on expanded notation.

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An exponent is when a little number is to the right and a bit above a number.  It's also called a "power."  Here are a couple examples of what it means:

3^2 = 3 x 3= 9   and 2^4 = 2 x 2 x 2 x 2 = 16

For more info on how exponents work in Algebra, check out my lesson on exponent rules.  (There are several individual lessons, this is just the review lesson.)

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From Algebra, an exponential is a function in the form:

            where (in my picture) b > 1

The graph of this exponential on the right.  The bigger x gets, the faster the graphclimbs!  Notice that the variablex, is up in the exponent...  The base of the exponential isb.  The bigger the base, the faster the graph climbs!
For more info, check out my lesson, The Exponential Monster.

the graph of an exponential

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Exterior Angles
When a pair of parallel lines are intersected with a transversal, angles ABG andH are the exterior angles that are formed.  Exterior angles are on the outside!

exterior angles

A B C D E F G H I no 
N O P Q R S T U V W no