Download Acute Angle - K6 Geometric Shapes

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Geometry Dictionary
Acute Angle:
Any angle measuring greater than 0° and less
than 90°
Acute Triangle:
A triangle where ALL THREE angles are acute
angles. See Acute Angle
Adjacent Angles:
Angles that are IMMEDIATELY next to each
other.
Adjacent Sides:
Sides of a shape that are IMMEDIATELY next to
each other.
Align:
When you arrange items in a straight line. You
can align edges or even center points of shapes.
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Alternate:
Angles opposite each other when created by
drawing a transversal line. See Transversal Line
Altitude:
The perpendicular distance from the highest
vertex of a shape to the shapes base line.
Angle:
The amount of rotation, in an anti clockwise
direction, between two intersecting lines,
measure by degrees.
Angle Bisector:
The name given to a line, line segment or ray;
that divides an angle into two equal parts.
Angle of Rotation:
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The number of degrees an object is rotated
around a fixed point. This is always measured
in a clockwise direction.
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Anti-Clockwise:
The opposite direction to the way the hands on
an analogue clock move.
Also known as counter clockwise.
Apex:
The highest point on a two dimensional (2D) or
three dimensional (3D) shape.
Arc:
A section of a curve, or part of a circle.
Area:
The amount of SURFACE a shape occupies –
measured in square units.
Asymmetry:
A shape that does not have sides exactly the
same.
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Attribute:
This is a characteristic. Attributes can be color,
size, shape or any other distinguishing
characteristic. We usually sort according to
attribute.
Axis:
This can be a real or an imaginary reference
line.
Axis of Symmetry:
This is the line that divides symmetrical shapes
in half.
Base:
This can be the bottom line of a two
dimensional shape, or the bottom face of a
three dimensional figure.
Bi-:
This is a prefix meaning two or twice of
something. An example: Bicycle – two wheels.
Bisect:
To divide into two equal parts.
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Bisector:
A line, point or plane that divides something
into two equal parts.
Boundry:
A line creating the outside edge of a shape. It is
also known as the perimeter.
Breadth:
The distance from one side of a shape to its
other side. Sometimes referred to as ‘width’.
Calculate:
To perform mathematical operations.
Calculator:
A device used to perform mathematical
operations.
Capacity:
The amount a container can hold. Usually
measured in cubic units.
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Carroll Diagram:
A sorting diagram named after Lewis Carroll.
Cartesian Plane:
Also called the coordinate plane. Contains two
perpendicular axis – X-Axis and Y-Axis. Points are
plotted taking a position from both the X and Y
axis. The X-Axis is always listed first. e.g. (3,10)
Chord:
A line segment connecting two points on a circles
perimeter.
Circle:
A plane shape drawn by a line whose points are
equidistant from any given point. A circle is a
closed curve.
Circumference:
The distance around (the boundary or perimeter) a
circle. Calculated by equation: P = 2πr
Clockwise:
The direction the hands on an analogue clock move.
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Closed Curve:
Any curve where it joins itself at its starting point.
Cointerior Angles:
The inner angles on the SAME SIDE of a line drawn
across to parallel lines.
Colinear:
When objects are situated on the same line.
Colinear Points:
Three or more points that lie on the same line.
Compass:
An instrument used to create circles
Complimentary Angles:
Two angles whose SUM equals 90°
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Concave:
Curved inwards. The opposite of convex.
Concave Quadrilateral:
A quadrilateral with at least one reflex angle.
Concave Polygon:
A polygon with at least one reflex angle.
Concentric Circles:
Circles different in size, but sharing a center point.
Cone:
A solid shape composed of a circular or elliptical
base, and a curved surface which tapers to a vertex.
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Congruent Figures:
A congruent figure has all equal sides and all equal
angles.
Converging Lines:
Lines that all head in the direction of the same
point.
Convex:
Curved outwards – the opposite of concave.
Convex Quadrilateral:
A quadrilateral where no angles are greater than
180° (reflex)
Coordinates:
Pairs of letters or numbers indicating a points
position on the Cartesian/coordinate plane. These
are always indicated with the X-Axis value first
followed by the Y-Axis.
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Coordinate Plane:
See Cartesian Plane.
Coplanar:
Geometric objects that exist on the same plane.
Corner:
The points where surfaces/vertices meet.
Corresponding Angles:
Angles that have the same position created by one
line intersecting two or more parallel lines.
Counter Clockwise:
See Anti Clockwise
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Cross Section:
The face that results when a solid shape is cut.
Cube:
A solid form whose shape is created by six
congruent squares. A Cube is also a Platonic Solid.
Cubic:
The term used when describing a unit of volume.
Cuboid:
A right prism created by six regular faces. If all faces
are square it is said to be a cube.
Curve:
A line that is NOT straight.
Cyclic Quadrilateral:
A quadrilateral where a circle can be circumscribed
to contain ALL four vertices.
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Cylinder:
A solid shape composed of two congruent circles
and one curved surface.
Deca-:
Prefix meaning 10.
Decagon:
A 10 sided polygon.
Decahedron:
A polyhedron with 10 faces.
Decrease:
To make smaller in size.
Deduct:
To subtract or take away.
Degree:
The unit which angles are measured by.
Diagonal:
A line joining two NON adjacent vertices.
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Diameter:
A line connecting two points on a circle which also
INCLUDES the central point of the circle.
Diamond:
A plane shape with 4 equal sides and NO right
angles. Also known as a Rhombus.
Distance:
The length between two points or objects.
Divisible:
Can be divided without remainders.
Dodeca:
Prefix for 12.
Dodecagon:
A polygon with 12 straight edges.
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Edge:
Where two surfaces intersect or join.
Elipse:
An oval shaped plane shape, resembling a flattened
circle.
Endpoint:
The point denoting the end of a line segment.
Equation:
This is a mathematical statement containing an
equal sign showing that two expressions have the
same value.
Equiangular:
A shape that has all angles equal. All Regular
polygons are equiangular.
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Equilateral:
A triangle whose sides are all the same length.
Euler’s Formula:
For any convex Polyhedrons surface, Euler’s Formula
states: V – E + F = 2 where V,E & F are vertices,
edges and faces.
Exterior Angles:
The angle formed on the outside of a Polygon, when
one side is extended.
Face:
The flat surface of a three dimensional shape.
Finite:
Something that can be counted. It has a definite
beginning and end. The opposite of infinite.
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Flat:
A shape that has no depth.
Flip:
To turn over. Flip is a term used to describe one
type of geometric transformation.
Formula:
A rule, usually containing symbols (as it is true for all
cases) and describes the relationship between
quantities.
Geometry:
One of the two earliest areas of math to be studied.
(The other was numbers). It studies the shapes,
solids, points, lines, rays and curves and their
relationship in space.
Graph:
A drawing or diagram used to represent data. There
are many types of graphs – this image shows a line
graph.
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Graph Paper:
Paper pre-printed with a specific scaled grid for ease
of graph drawing.
Half:
One of two equal parts. When an object is cut into
two equal parts, each portion is one half.
Height:
The perpendicular distance from the top of an
object to the bottom/base.
Hemisphere:
A solid shape that is one half a sphere.
Hepta - :
A prefix meaning 7.
Heptagon:
A polygon with 7 sides.
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Heptahedron:
A polyhedron with 7 faces.
Hexa-:
A prefix meaning 6.
Hexagon:
A polygon with six sides.
Hexahedron:
A polyhedron with six faces.
Horizontal:
The opposite of vertical. In geometry, a line is said
to be horizontal if it is parallel to the X-Axis. In this
image the base of the front triangular face of the
tent is horizontal.
Hypotenuse:
The longest side of a right angled triangle.
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Icosa-:
Prefix meaning 20.
Icosagon:
A polygon with 20 sides.
Icosahedron:
A polyhedron made up of 20 faces.
Increase:
To make larger in size.
Infinite:
No definite end. The opposite of finite.
Infinity:
Unable to be counted – it has no end.
Interior Angles:
1: An angle within a polygon.
2: Angles within two lines, created when crossed by
a third (transversal) line.
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Intersect:
Where lines cross one another. The point the lines
have in common is called the point of intersection.
Irregular Polygon:
A shape that does NOT have all sides equal or all
angles equal is said to be an Irregular Polygon.
Isometric:
To have equal dimensions or measurement.
Isometric Paper:
Paper created with dots (dot paper) or grids (grid
paper) to assist with isometric drawings.
Isosceles Triangle:
A triangle that has two sides equal in length. Its
base angles are also equal in measure.
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Kite:
A plane shape – a quadrilateral, with two sets of
lines equal in length and one set of equal angles.
The lines joining opposite angles ALWAYS intersect
at 90°
Length:
Distance from one end to another.
Line:
An infinite set of points going in opposite directions,
with an angle of 180°
Line of symmetry:
An object or shape has a line of symmetry if it can
be divided into two equal and identical parts by that
line.
Line segment:
A section of a line with a beginning and end point.
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Maximum:
Greatest value or amount. Highest point
Measure:
Use of standard units to measure size or quantity.
Measurement can be made of length, area, weight
(mass) volume, temperature and time.
Measurement:
The exact measure of an object or quantity.
Mono-:
Prefix for 1.
Nona-:
Prefix for 9.
Nonagon:
Polygon with 9 sides.
Numerals:
Symbols used to represent a number.
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Oblique:
Lines at an angle to the X-Axis (Horizon)
Oblique Prism:
A prism with bases NOT aligned directly above each
other.
Obtuse Angle:
Any angle greater than 90° and less than 180°
Obtuse Triangle:
A triangle that contains one obtuse angle.
Octa-:
A prefix meaning 8.
Octagon:
A polygon with 8 sides.
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Order of Rotation:
How many times an outline matches its original
during one full rotation.
Ordered Pair:
Ordered Pairs are used to indicate a points position
in geometry. (3,1) is NOT the same as (1,3). The
ORDER is essential.
Origin:
The point of intersection of the X-Axis and the Y-Axis
on the Cartesian plane.
Paralell lines:
Lines that will NEVER intersect.
Parallelogram
A quadrilateral with opposite sides equal in length,
and parallel.
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Pattern
A repetition of objects.
Penta-:
Prefix for 5.
Pentagon:
A polygon with 5 sides.
Pentahedron:
A polyhedron with 5 sides.
Perimeter:
The outline of a two dimensional shape.
Perpendicular:
Two lines that meet at 90° are said to be
perpendicular.
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Perpendicular Bisector:
A line that intersects a line segment at 90° AND
bisects the line segment.
Pi:
The ratio of a circles circumference to its diameter.
The exact value of pi is yet to be identified. When
calculating with Pi, it is traditional to leave in symbol
form, use the value of 22/7 or use the value 3.14
Plane Shape:
A flat shape with only two dimensions, height and
width. It has no depth.
Platonic Solid:
Five Regular Polyhedra made only with either
equilateral triangles, squares or pentagons. The five
are: Cube, Tetrahedron, Octahedron, Icosahedron
and the Dodecahedron.
Poly-:
Prefix for many.
Polygon:
A plane shape with three or more straight lines.
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Polyhedron:
A Three dimensional object made up of plane
shapes.
Position:
Where something is when compared to another
object or its surroundings.
Prism:
1: Right Prism: A three dimensional shape made up
of two identical plane shapes, and all other faces are
rectangles.
2: Oblique Prism: See Oblique Prism.
Protractor:
An instrument used during geometric drawings to
measure the degrees of angles
Pyramid:
A three dimensional shape composed of a polygon
as its base, and all other faces congruent triangles
that meet at the top (a common vertex)
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Pythagoras:
A Greek Mathematician who lived circa 500BC.
Famous for his theorems on the Right Angled
Triangles.
Pythagorean Theorem:
In a right angled triangle, the square of the
hypotenuse is equal to the sum of the squares of the
other two sides.
Quadrangle:
A polygon with 4 sides and 4 angles.
Quadrant (Circle):
A quarter of a circle, or a quarter of a circles
circumference.
Quadrant (Cartesian Plane):
Any quarter of the plane made by the intersection
of the X and Y-Axes.
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Quadrilateral:
A polygon with 4 sides.
Quarter:
One of four equal parts.
Radius:
Distance from the center to the circumference of a
circle.
Ratio:
A comparative value of two or more amounts.
Ray:
A line with a start point but no end point.
Rectangle:
A quadrilateral with 4 right angles and two sets of
parallel lines.
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Rectangular Prism:
A polyhedron with two identical rectangular faces,
joined by all other faces which are congruent. Also
known as a cuboid.
Reflection:
A mirror image.
Reflex Angle:
Any angle measuring between 180° and 360°
Revolution:
One complete turn through 360°
Rhombus:
A quadrilateral with 4 equal sides, and where
opposite angles are equal. See Kite also.
Right Angle:
An angle measuring 90°
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Rotation:
To turn an object.
Rotational Symmetry:
If, when an object is rotated, it has the SAME
OUTLINE as its original shape, it is said to have
Rotational Symmetry.
Scale:
To enlarge or reduce an object.
Scalene Triangle:
A triangle where all three sides have DIFFERENT
lengths.
Sector:
A section of a circle defined by two radii and an arc.
Segment:
A section of a circle defined by a chord and an arc.
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Semi Circle (Half Circle):
Half a circle.
Septa-:
Prefix for 7.
Septagon:
A polygon with 7 sides.
Shape:
A form or outline of an object.
Side:
The line or curve on the outside of a shape that joins
the shapes vertices.
Size:
How big or small something is.
Solid:
A three dimensional shape.
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Solution:
Answer to a problems.
Sphere:
A 3-Dimensional solid where all surface points are
equidistant from a given point which is its center.
Square:
A quadrilateral with 4 sides equal in length, AND 4
right angles.
Straight Angle:
Any angle that equals 180°
Straight Line:
The shortest distance between two points.
Supplementary Angle:
Two angles whose sum is 180°
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Surface:
A set of points that define a space. A surface can be
curved or flat.
Surface Area:
The total area of ALL surfaces of a three dimensional
figure.
Symmetry:
An object has symmetry when one half is a mirror
image of the other half.
Tangent:
A straight line that touches a circle at ONLY one
point.
Tangram:
A square cut into seven pieces.
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Tessellation:
Patterns created from shapes that fit together with
NO gaps.
Tetrahedron:
A polyhedron with four triangular faces. It is one of
the five Platonic Solids. See Platonic Solid also.
Three Dimensional (3D):
Has three dimensions – Length, Breadth (width) and
Height.
Transformation:
A change in position or size. It can be created by
flipping, rotating, translating or enlarging.
Translation:
To move an object in any direction without rotating
it.
Trapezium:
A quadrilateral with NO parallel sides.
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Tri-:
Prefix meaning three.
Triangle:
A three sided polygon.
Triangular Prism:
A prism whose two bases are congruent triangles
and all other faces (3) are congruent rectangles.
Turn:
Rotate around a fixed point.
Turning Symmetry:
Rotating an object about a point.
Two Dimensional (2D):
Having only two dimensions; Length and Breadth.
Uniform Cross Section:
When a solid undergoes a cross section, and the
new resulting face is the same size as the solids
base, the cross section is said to be Uniform.
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Vertex:
The point where sides or surfaces meet to create a
corner.
Vertical:
At right angles to the horizon, or the X-Axis on the
Cartesian Plane. In this image, the telephone poles
are vertical.
Vertically Opposite:
Directly opposite.
Volume:
The capacity of a three dimensional object
measured in Cubic Units.
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Width:
Also known as breadth. The distance from one side
of a shape to the other.
X-Axis:
The horizontal axis of the Cartesian Plane.
X-Coordinate:
The first element of an ordered pair. The position of
a point in relation to the X-Axis. In the example
(3,10) the value of the X-coordinate is 3.
Y-Axis:
The vertical axis of the Cartesian Plane.
Y-Coordinate:
The second element of an ordered pair. The
position of a point in relation to the Y-Axis. In the
example (3,10) the value of the Y-coordinate is 10.
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