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Online Math Dictionary: S

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!
 

scalene triangle scientific notation secant
sector of a circle segment
(line segment)
semi-circle
semiannual sequence series
set similar triangles sine
slope of a line snub
cuboctahedron
snub
icosidodecahedron
sphere square square numbers
square root subset subtrahend
sum summation supplementary 
angles
supplement 
of an angle
symmetric system of equations

 

Scalene Triangle
scalene triangle is a triangle where no twosides are the same length.
For information on triangles, check out Types of Triangles
 

scalene triangle

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Scientific Notation
Scientific notation is a way to write a number as the product of a number between 1 and 10 and multiple of 10.
Examples:
23,000 = 2.34 x 10^4     .0067 = 6.7 x 10^-3

 

Secant
From trigonometry, the secant of an angle (in the picture below) is the ratio of the hypotenuse to the adjacent side:
secant(theta) = hypotenuse / adjacent = r/x     secant(theta) = 1 / cosine(theta)
For more trig info, check out my reference sections on The Trigonometry of Circles and The Trigonometry of Triangles.

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Sector of a Circle
sector of a circle is a pie shaped portion of the area of the circle.  The piece of pie is betweentwo segments coming out of the center of the circle.

For more information on circles, check out my reference sections on The Geometry of Circles and The Trigonometry of Circles.

sector of a circle

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Segment - Line Segment
A line segment is the finite piece of line that connects two points in space.
line segment

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Semi-circle
A semi-circle is half of a circle.

semi-circle

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Semiannual
A term often used in Algebra money problems, semiannually means twice a year.
For information on how to solve compound interest problems, check out my lessons on Exponentials and Logarithms.

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Sequence
A sequence is a list of numbers that typically changes according to some sort of pattern.
finite sequence example:  1, 3, 5, 7, 9
An infinite sequence example:  1, 4, 9, 16, 25, ...
For more info on sequences, check out my lessons on Sequences & Series.

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Series
A series is the sum of a sequence.
Example:  1 + + + + 25
For more info on sequences, check out my lessons on Sequences & Series.

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Set
set is a group of objects:
Set A
Set A

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Similar Triangles
Similar triangles are triangles whose corresponding angles are congruent and whose sides are proportional (see the equivalent fractions to the right).
similar triangles   a/d = b/e = c/f    d/a = e/b = f/c

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Sine
From trigonometry, the sine of an angle (in the picture below) is the ratio of the opposite side to the hypotenuse:
sine (theta) = opposite / hypotenuse = y / r         sine (theta) = 1 / cosecant (theta)
For more trig info, check out my reference sections on The Trigonometry of Circles and The Trigonometry of Triangles.

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Slope of a Line
Basically, the slope of a line tells us how steep a line is and whether it's going up or down (increasing or decreasing).  The slope is found by looking at the rise over therun.

slope = rise / run
For more specific info on how to find slopes, check out my Algebra lessons on lines.

slope of a line

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Snub Cuboctahedron
The snub cuboctahedron is created by either truncating (cutting off) tips 
of the cube or the octahedron.

     Properties of the snub cuboctahedron
     38 total faces: 32 equilateral triangles and 6 squares
     24 vertices where each is 4 triangles and 1 square
     60 edges
     Dihedral angle
142 degrees, 59 minutes for the sqr-tri angle and 
                                   153 degrees, 14 minutes for the tri-tri angle

For more info about polyhedra, check out my Platonic solids gallery.

Snub Cuboctahedron

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Snub Icosidodecahedron
The snub icosidodecahedron is created by either truncating (cutting off) 
the dodecahedron or the icosahedron.

     Properties of the snub icosidodecahedron
     92 total faces: 80 equilateral triangles and 12 regular pentagons
     60 vertices where each is 5 triangles and 1 pentagon
     150 edges
     Dihedral angle
152 degrees, 16 minutes for the pent-tri angle and 
                                   164 degrees, 11 minutes for the tri-tri angle

For more info about polyhedra, check out my Platonic solids gallery.

snub icosidodecahedron

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Sphere
A sphere is a three dimensional circle.  Imagine putting a line through the widest part of a circle and spinning it.  This would give you a sphere.

sphere

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Square
square is a regular quadrilateral which means that all its sides are the same length (congruent) and all its angles are the same size (congruent) (they have to all be 90 degrees.)

For more information on squares, check out my Properties of Squares reference page.

square

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Square Numbers
A square number is the answer when you take an integer and multiply it to itself:
square numbers     1 x 1 = 1^2 = 1     2 x 2 = 2^2 = 4      3 x 3 = 3^2 = 9      4 x 4 = 4^2 = 16
Here's a partial list of square numbers:  
    01491625364964, 81100121144, ...

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Square Root
Here is how we write a square root...  It's made up of a radical sign and something inside called the radicand.
the square root of x

The square root of a number (the radicand) is a number that produces the radicand when it is squared.  
Example:   


sqrt (9) = 3   where 3 x 3 = 9
To learn more about radicals, check out my Radicals Review lesson.

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Subset
A subset is a set whose members are part of a bigger set.  
Example:  The set B is a smaller set whose members are part of the bigger set A:
Set A and Set B
Here's how we write it...  
The "U" lying on its side is the symbol for "is a subset of."     
So, this says that the set B is a subset of the set A.

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Subtrahend
When you do a subtraction problem, the subtrahend is the number you are taking off:
                      8 5 = 3
For more info, check out my Subtraction Lessons.

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Sum
In an addition problem like   2 + 3 = 5,   the sum is the answer
For more info, check out my Addition Lessons.

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Summation
A summation is a fancy notation to represent a series (a list of things that you want to add together.)
Here's an example:
The summation from i = 1 to 4 of  i^2 = 1^2 + 2^2 + 3^2 + 4^2 = 1 + 4 + 9 + 16 = 30
The complete description is pretty long...  If you want more than this, check out my Summations Algebra Lesson on Sigma Notation.

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Supplementary Angles
In the picture on the right, angles A and B are supplementary angles because their measures add up to 180 degrees:
the measure of angle A + the measure of angle B = 180 degrees

supplement of an angle

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Supplement of an Angle
Working from the idea of supplementary angles in the definition above this, the supplement of an angle B is whatever size is necessary so that, if you stick the two angles together, they make a 180 degree angle.

To find the supplement of an angle, just subtract from 180... 
Example:  Find the supplement of angle B whose measure is 40 degrees:
   180 - 40 = 140...  So, the supplement  is 140 degrees.  Easy!

supplementary angles

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Symmetry
Having symmetry (or being symmetric) means that something is a mirror image over a line in space.  Look at the picture on the right...  The left halfis a perfect mirror image of the right half over that yellow line.  (Ignoring the color difference, of course.)
You can say that this image is symmetric with respect to the line...  Or you can say that this image is symmetric over the line (more casual).  The line is called the axis of symmetry.

a symmetric image

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System of Equations
A system of equations is when you have more than one equation AND more than one variable to solve for (the unknowns).  
Example:     2x  5y 22
              7x + 3y -5

For information on how to solve systems of equations, check out my Systems of Equations Lessons for 2x2's and mySystems of Equation Lessons for 3x3's.

 

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