1. Welcome to Geometry!!!
One thing that is different about
geometry is the amount of vocabulary you
need to "master".
It is a lot, but it's not impossible.
2. Point: An exact location in space.
Usually represented with a "." in math
problems and examples.
In our room examples:
the dot on the i in scottish on the clock.
the corners (vertex) of pennant, book,
piece of paper.
3. Line: A straight path of points that go on and on
in both directions.
Represented with
In math problems and examples
Sort of examples of lines (line segments) in our
room:
Where the wall meets the ceiling
The edge of a desk
grids on the ceiling
top of the chalkboard
the edge of most posters or pieces of paper
4. Plane: A surface with only 2
dimensions.
Examples of planes in our room.
coverings of ceiling lights
Floor
A whiteboard
Smart board screen
ceiling
5. Types of Lines:
Parallel : Lines that never cross
Examples:
top and bottom edge of smart board, chalkboards,
and most whiteboards.
Intersecting: Lines that cross at one point:
Examples:
edges of the pennants, the edges of the stars on
the American Flag, top edge of north and south
walls
Perpendicular: Lines that intersect at right angles.
Examples:
6. Angle: A figure formed by two line
segments or rays that have same endpoint.
Or at the intersection of lines.
angle
7. Acute angle: an angle less than a right angle.
Think small and 'cute'
Right Angle: An angles that measures 90
degrees (right angle)
Obtuse Angle: An angle greater than a right
angle. Think Ob, Obese (fat)
8. Polygon: A closed figure made of line
segments:
Examples of Polygons:
Not Polygons:
Closed, but not line segments Line Segments, but not closed
9. Triangles: A polygon with 3 sides
We name triangles by angles and side
lengths.
For example the red triangle above is
a right isosceles triangle
Huh?
10. Naming triangles by angle types
1) Right Triangles have a right or 90 degree angle in
them.
Angle BCA is right ... the little square is a 'math
note' that means right angle.
2) Acute Triangles have all acute or less than 90
degree angles in them.
See how all the angles are acute.
3) Obtuse Triangles have 1 obtuse or larger than 90
degree angle in them. A
Angle ABC is an obtuse angle B
C
11. Naming Triangles by side lengths
Scalene Triangles have no congruent (same size)
sides (and not congruent angles) A
B
None of the sides are congruent
C
Isosceles Triangles have 2 congruent sides (and
2 congruent angles)
Side GH and Side GI are same length,
the little 'hash marks' are a 'math note'
saying that.
Equilateral Triangles have 3 congruent sides (and
3 congruent angles)
The little 'hash marks' show all sides
are the same length.
12. Putting it all together.
Look at the triangle below
Start with angle type:
Right ...
Then look at side lenghts:
Scalene
So ABC is a right scalene triangle
14. Quadrilaterals: Four sided polygons.
Like triangles, special quadrilaterals can be
named or classified by sides and angles.
Look at the next page, to see how this is
done.
15. Special Quadrilateral Types
related oddball
See how the definitions are so similar in these 4.
Trapezoid:
Parallelogram: Both sets of opposites are parallel. Opposite
sides are congruent. Opposite angles are congruent. Only one set of
opposite sides
Rectangle: Both sets of opposites are parallel. Opposite is parallel.
sides are congruent. All angles are right angles.
Rhombus: Both sets of opposites are parallel. Opposite
sides are congruent. All sides are congruent
Square: Both sets of opposites are parallel. All angles are
congruent. All angles are right angles.
