1. February 08, 2013
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.
2. February 08, 2013
Topic 9: Lines, Shapes and Angles (2D Geometry)
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.
3. February 08, 2013
Topic 9: Lines, Shapes and Angles (2D Geometry)
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 (90º)
Square Symbol is frequently used to show a right angle
Note: The terms parallel, intersecting and perpendicular can
be used with rays and line segments.
4. February 08, 2013
Topic 9: Lines, Shapes and Angles (2D Geometry)
Important Terms: Digging Deeper with Angles
Acute Angle: An angle that measures less than 90º
(0º < Acute Angle < 90º)
acute is like "cute"
Right Angle: An angle that measures exactly 90º
(Think corner of a square)
Obtuse Angle: An angle that is greater than 90º
(90º < Obtuse Angle < 180º)
obtuse is like obese
5. February 08, 2013
Topic 9: Lines, Shapes and Angles (2D Geometry)
Important Terms: Creating Shapes with Angles and Line Segments
Polygon: A closed figure (shape) that only has line segments for
sides.
Polygons Not Polygons
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
6. February 08, 2013
Topic 9: Lines, Shapes and Angles (2D Geometry)
Focus on Triangles:
Triangles are named by their angle types and side lengths
Angle Naming Side Naming
7. February 08, 2013
The best possible names for triangles use both angle and
side names. Exception is equliateral
acute scalene: all acute angles, no sides congruent
acute isosceles: all acute angles, 2 sides congruent
equilateral: all acute angles, all sides congruent
right scalene: one right angle, no sides congruent
right isosceles: one right angle, 2 sides congruent
obtuse scalene: one obtuse angle, no sides congruent
obtuse isosceles: one obtuse angle, 2 sides congruent
8. February 08, 2013
Topic 9: Lines, Shapes and Angles (2D Geometry)
Focus on Triangles:
Triangles are named by their angle types and side lengths
The best way 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.
9. February 08, 2013
Topic 9: Lines, Shapes and Angles (2D Geometry)
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.
"Congruent"
= same size
or same
length
10. February 08, 2013
Topic 9: Lines, Shapes and Angles (2D Geometry)
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
11. February 08, 2013
Best name: parallelogram
Properties: 1, 2
Properties to consider
1) 4 sides
2) pairs of parallel sides
3) congruent sides
4) right angles
12. February 08, 2013
Best name: rectangle
Properties: 1, 2, 4
Properties to consider
1) 4 sides
2) pairs of parallel sides
3) congruent sides
4) right angles
13. February 08, 2013
Best name:
square
Properties: 1,2,3, 4
Properties to consider
1) 4 sides
2) pairs of parallel sides
3) congruent sides
4) right angles
14. February 08, 2013
Best name: Rhombus
Properties: 1,2,3
Properties to consider
1) 4 sides
2) pairs of parallel sides
3) congruent sides
4) right angles
15. February 08, 2013
Best name: Quadrilateral
Properties: 1
Properties to consider
1) 4 sides
2) pairs of parallel sides
3) congruent sides
4) right angles
16. February 08, 2013
Best name: right scalene triangle
Properties:
Has a right angle
No sides are congruent
Best name: right isosceles triangle
Properties:
Has a right angle
2 sides are congruent
