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L1: Exploring Triangles
A triangle is a 2D shape which has 3 sides and 3 ___________ angles.
We can name triangles by the number of equal sides
An equilateral triangle: - has 3 equal sides
- 3 angles which are all 60 degrees
- 3 lines of symmetry
Eg:
An isosceles triangle:
- has 2 equal sides
- has 2 equal angles
- has 1 line of symmetry
Eg:
A Scalene triangle:
-has no equal sides
-has no equal angles
-has no line of symmetry
Eg:
Textbook:
Page 201-204
Questions: 1-10
L2: Naming and Sorting Triangles by Angles
Remember: All angles in a triangle add up to 180 degree’s
- An acute triangle has all angles less than 90 degree’s
Eg:
- A right triangle has ONE 90 degree angle
Eg:
- An obtuse triangle has ONE angle greater than 90 degree’s
Eg:
Textbook:
Pg: 207-208
Questions: 1-8
L3 Drawing Triangles
You can use a ruler and a protractor to construct a triangle
Ex: Construct triangle ABC with the measures
Line BC = 3 cm
Angle B = 80 degrees
Line BA= 2.5 cm
Step 1:
Draw side AB
___________
B
C
Step 2:
Measure an 80 degree angle at point A
___________
B
C
Step 3
Draw side AC make it 2.5 cm
Step 4
Join C to B
Textbook
Page: 211-213
Questions: 1-9
L4: Investigating Polygons
Regular Polygon: that is equiangular (all angles are equal in measure) and
equilateral (all sides have the same length).
Irregular Polygon: A polygon that does not have all sides equal and all
angles equal.
Convex Polygon has all angles less than 180 degrees
Concave Polygon has at least one angle greater than 180 degrees
Textbook: 216-218
Questions 1-9
L5 Perimeters of Polygons
Perimeter= is the total distance around an object
We can find the perimeter of any polygon by adding the side lengths
Perimeter
= s+s+s+s+s+s
=5+3+6+2+3+3
= 22
Two formula to find the perimeter of some polygons
1- For a Regular Polygon all sides are equal so we can multiply.
Ex:
P=4XS
P=4X5
P = 20 m
2- For a Parallelogram we have two sets of equal side lengths (this works for a
rectangle as well)
Ex:
P = 2 X (l+s)
P = 2 X (2 +5)
P=2X7
P= 14 in
Textbook:
Page 229-230
Questions 1-3, 5-7, 9
L6 Congruence in Regular Polygons
Congruent:
means equal (exact) to
the
sign is
There are 2 ways to show that polygons are congruent
Option 1: Place one polygon on top of the other, if they match exactly
they are congruent.
Option 2: Compare the side and angle measures. If all sides are equal
and all angles are equal, the polygon are congruent.
Ex:
2 cm
2 cm
Textbook: Page: 222-223
Questions: 1-3, 5, 7
L7 Area of a Rectangle
Area: is the amount of surface a shape or region covers.
We measure area in square units.
Ex:
Formula:
Area = l X w
Example:
Symbolically:
Area = l X w
Area = 4 X 2
Area = 8 cm2
Pictorially:
2cm
4cm
1 2 3 4
5 6 7 8
2cm
4cm
Area = 8 cm2
Textbook: Pg 233
Questions: 1-4, 6, 10