Centroid of a
Triangle
The
centroid of a
triangle is kind of the center of the triangle
-- if you try to balance the triangle on the tip of
your finger, the centroid is where you'll put your
finger to keep it level. The
bisectors of each of
the angles of the triangle intersect in the
centroid. |
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Chord
A chord on a circle is
a line segment that connects
two points that are on the outside edge
(circumference) of the circle. |
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Circle
A
circle is the set of
points that all lie within a given distance of the
center of the circle. This given distance is
called the radius ( r
in the pic on the right ).
For more info on circles, check
out my Geometry of
Circles page. |
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Circumference
The circumference is
the perimeter (outer
edge) of a circle. The formula for finding the
circumference of a circle is:
circumference
=
where
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Circumscribed
In the picture on the
right, the circle is
circumscribed about the
triangle since each
vertex of the triangle is
touching the circle. |
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Clockwise
Clockwise is when you
are moving in the same direction as the arms on a
clock. |
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Coefficient
In a
polynomial, the
coefficients are the numbers that are right in front of the
letters (the
variables.)
Examples: In 5x-3y,
the coefficients are 5
and -3....
x+7
is really 1x+7
and the coefficient is 1.
For more info on coefficients, check out my algebra lesson on
Polynomials. |
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Column
A column is a
vertical stripe of
something.
Usually, in math, it's a
vertical stripe of
numbers. (Remember that "vertical" means up
and down.) |
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Combinations
Combinations count how
many different ways you can choose things from a set
of objects.
Example: If you have three employees (A,
B and
C) and you want to form
a committee of two, how many different ways can you
do it? 3 ways...
A and
B
A and
C
B and
C
For more info, check out my
Combinations lesson. |
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Combinatorics
Combinatorics is the
study of counting.
For more info, check out my
Combinatorics lessons. |
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Commutative
Property of Addition
The commutative property of addition is a math rule that is
always true. Here it is with letters:
a
+ b
=
b
+ a
This rule just says that, when you are doing
addition, it doesn't matter which order the numbers
are in. You can add a
and b OR you can add
b and a
... and you'll get the same answer. Here it is
with numbers so you can check this for yourself!
2
+ 3
= 3
+ 2
NOTE: This does not work
with subtraction! |
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Commutative
Property of Multiplication
The commutative property of
multiplication is a math rule that is
always true. Here it is with letters:
a
x b
=
b
x a
This rule just says that, when you are doing
multiplication, it doesn't matter which order the
numbers are in. You can multiply a
and b OR you can multiply
b and a
... and you'll get the same answer. Here it is
with numbers so you can check this for yourself!
2
x 3
= 3
x 2
NOTE: This does not work
with division! |
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Complementary Angles
Complementary angles
are NOT angles that say "Oh, what a nice shirt and I
just love the hair!" Those would be
"complimentary
angles" spelled with an "i".
In the picture on the right,
angles A and
B are complementary
angles because their measures add up to
90 degrees:
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Complement of an
Angle
Working from the idea
of complementary angles in the definition
above this,
the complement of an
angle B is whatever
size is necessary so that, if you stick them
together, they make a 90
degree angle.
To find the complement
of an
angle, just subtract from 90...
Example: Find the complement of
angle B whose measure
is 30 degrees:
90 -
30 =
60... So, the
complement is 60 degrees.
Easy! |
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Complex Numbers
Before you hit algebra
(and through most of algebra), you work with the
Real Number
System which is just all those regular numbers you're used
to working with: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. This
includes fractions, decimals and radicals made from these
numbers. BUT, there is another number system out
there! No, not THAT! Yes, it's all too
true... It's the Complex Number System where a complex
number is in the form:
In higher math, you can do
arithmetic,
algebra and more
with these goofy numbers. AND you can make very cool
computer art with them --
Fractals. Check out my
fractal gallery to learn more.
For more info on complex numbers, check out my algebra
lessons on
complex numbers. |
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Composite
A
number is composite if it has more than two
factors.
The number 20 is composite since it has more than
two factors: 1, 2, 4, 5, 10, 20. The
number 5 is NOT composite since it only has two
factors: 1 and 5. The number
5 is
prime. The
number 1 is neither prime nor composite since it
only has one factor: 1. |
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Concave Polygon
Technically, if you
can connect two
vertices
(the corners) of a
polygon and have all or part of
the line go OUTSIDE
the polygon, then the
polygon is concave. I just remember that, if
there is a cave (like the kind a bear lives
in), then it's concave. |
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Cone
Ah, memories of
childhood and ICE CREAM CONES! Wait, that was
just last week. What was I talking about?
In geometry, a
cone is formed by
taking a
circle (or an
ellipse), and a line
going up from the middle of the
circle... Then
a surface joins the top of the
line and the edge
of the circle. The cone in my picture on the
right is a "right circular cone" since the
line forming the height
shoots up in a
right angle (90 degrees) to the
base
(the circle.)
For info on conic sections, check out my
conic sections lessons. |
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Congruent
Two
objects are congruent if they are the same size and
shape. In the pics on the right,
We use an
equal sign with a
little squiggle on top
for the notation for congruent. |
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Conjugate
You'll see conjugate
pairs when working with
radicals and
complex numbers.
I like to call them conjugate buddies, because they usually
need to be with their friend in an algebra problem. Conjugate
buddies are the same, but with the opposite sign. Here
are two examples:
For more info on conjugates and how
the complex kind are used in Algebra, check out my lesson on
complex zeros. |
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Consecutive
Consecutive just means
one right after the other.
Example: A list of
consecutive whole numbers: 0, 1, 2, 3, 4, 5, 6, ...
Example: A list of
consecutive even whole numbers: 0, 2, 4, 6, 8, ...
Example: A list of
consecutive odd whole numbers: 1, 3, 5, 7, 9, ...
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Convex Polygon
You might want to
scroll up and check out the definition of
concave to really
understand this one. It's easiest
to just say that a convex
polygon is one that is NOT
concave! But, I'll let you think about this... A
polygon is convex if you can draw straight lines
that connect every single vertex and your lines
never go outside the polygon. There is no
cave! |
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Coordinate
This is the same thing
as
Cartesian Coordinates...
Coordinates on the Cartesian
plane are a set of numbers officially called "an
ordered pair" that are in the form
(
x
, y
) ... The x
guy is how far to the right or left you've counted
over... and the y guy
is how far up or down you've counted.
For more info on graphing with
Cartesian coordinates, check out my
Plotting Points lesson. |
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Coplanar
Any objects that lie
in the same plane are called coplanar. |
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Corresponding Sides and Angles
It's easier to show
you this one than to tell you what it is in words.
In similar triangles, like the ones in the picture
on the right... One set of corresponding sides
are A and
D... One set of
corresponding angles are a
and d.
Corresponding objects are in the same location. |
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Counter-Clockwise
Counter-clockwise is
when you are moving in the opposite direction as the
arms on a clock. |
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Cramer's Rule
Cramer's Rule is a
method in algebra to solve systems of equations.
For more info on Cramer's Rule, check out my full lessons:
Cramer's Rule for 2x2 Systems and
Cramer's Rule for 3x3 Systems |
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Cube
A cube is a box formed
by putting six squares together, connected at the
edges. Since all faces of a cube are squares,
all the edges of the cube are the same length (which
is 5 in my picture on
the right.)The
cube is one of the five Platonic Solids.
For more info
about Platonic solids, check out my
Platonic solids gallery. |
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Cubic Equation
Used in Algebra, the
critter below is cubic because
of the x cubed and an
equation because of the
equal sign.
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Cubic Polynomial
Used in Algebra, the
critter below is a cubic
polynomial because
of the x cubed.
For more info on polynomials, check
out my lesson,
What's a Polynomial? |
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Cuboctahedron
The cuboctahedron is
one of the semi-regular Platonic solids (a
polyhedron.)
It is created by either
truncating
(cutting off) the cube one
half of the way into each edge or
by truncating the
octahedron one half of the way into each
side.
Properties of the
cuboctahedron:
14
faces: 8 equilateral triangles and 6 squares
12 vertices: 2 triangles, 2 squares
24 edges
Dihedral angle:
about 125.27 degreesFor more info about
Platonic solids, check out my
Platonic solids gallery. |
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Cylinder
A cylinder is formed
by taking two circles (or ellipses), putting one up
above the other and wrapping a surface around to
connect the edges. |
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