topic 9 important terms

8/8/2019 Topic 9 Important Terms

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January 18, 20

Topic 9: Lines, Shapes and Angles (2D Geometry)

Important Terms:

Point: A definite location in space.

Line: A series of points that goes forever in both directions.Plane: an infinitely large 2 dimensional (flat) surface.

Points and lines "rest" on a plane. A solid shape, like a

cube has multiple planes. Each face of the cube is its own

plane.

Line: A series of points that goes forever in both directions


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January 18, 20


Important Terms: Digging Deeper with Lines

Line Segment: Part of a line, has endpoints

Ray: Part of a line that has one endpoint, other end

continues forever in one direction.

Angle: 2 rays or line segments that meet at a common

point.


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January 18, 20


Important Terms: Digging Deeper with Lines

Parallel Lines: 2 lines that never intersect

Intersecting Lines: 2 lines that cross paths

Perpendicular lines: 2 lines that intersect at a right angle (90)

Note: The terms parallel, intersecting and perpendicular can

be used with rays and line segments.

Square Symbol is frequently used to show a right angle


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January 18, 20


Important Terms: Digging Deeper with Angles

Acute Angle: An angle that measures less than 90

(0 < Acute Angle < 90)

Right Angle: An angle that measures exactly 90

(Think corner of a square)

Obtuse Angle: An angle that is greater than 90

(90 < Obtuse Angle < 180)


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January 18, 20


Important Terms: Creating Shapes with Angles and Line Segments

Polygon: A closed figure (shape) that only has line segments for

sides.

Triangle: A 3-sided polygon

Quadrilateral: a 4-sided polygon

Pentagon: a 5-sided polygon

Hexagon: a 6-sided polygon

Octagon: an 8-sided polygon

Polygons Not Polygons


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January 18, 20


Focus on Triangles:

Triangles are named by their angle types and side lengths

Angle Naming Side Naming


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January 18, 20


Focus on Triangles:

Triangles are named by their angle types and side lengths

The bestway to name a triangle is with both the angle name and side

name:

Acute Isosceles Obtuse Scalene Right Isoceles

all acute angles 1 obtuse angle 1 right angle

2 equal sides 0 equal sides 2 equal sides

Special Case!

An Equilateral Triangle is a triangle with 3 equal sides. You don't need to

call it an "Acute Equliateral", it's just an Equilateral.


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January 18, 20


Focus on Quadrilaterals

Quadrilaterals are 4-sided polygons

Quadrilaterals are classified or named by how their sides relate to each other.

We need to use the most specific name.


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Focus on Quadrilaterals

The sequence below might help to show why when we name a quadrilateral we need to

use the most specific name.

yes

yes

yes

yes

YES! .... and the most specific name


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January 18, 20


One last thing to remember. Really knowing what all the

terms on the previous pages are only partof what we need

to be able to do as learners.

So, while it is important that we know what a line segment is

or what a trapezoid is, we will also be working a great deal

on how to apply the knowledge of these geometrical terms.

topic 9 important terms

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