Lesson 8 ~ The Concept of Area ~ Areas of Rectangles and Squares ~ Areas of Triangles ~ Areas of Circles ~ Areas of Parallelograms and Trapezoids - PowerPoint PPT Presentation

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Lesson 8 ~ The Concept of Area ~ Areas of Rectangles and Squares ~ Areas of Triangles ~ Areas of Circles ~ Areas of Parallelograms and Trapezoids

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Lesson 8 ~ The Concept of Area ~ Areas of Rectangles and Squares ~ Areas of Triangles ~ Areas of Circles ~ Areas of Parallelograms and Trapezoids Example 8.4 – PowerPoint PPT presentation

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Title: Lesson 8 ~ The Concept of Area ~ Areas of Rectangles and Squares ~ Areas of Triangles ~ Areas of Circles ~ Areas of Parallelograms and Trapezoids

1
Lesson 8The Concept of AreaAreas of
Rectangles and SquaresAreas of
TrianglesAreas of CirclesAreas of
Parallelograms and Trapezoids
Example 8.1
Example 8.5
Example 8.2
Example 8.6
2
Lesson 8.B
Area ofRectangles and Squares
The area of a closed figure is the number of
square units contained in the figure.
4 units
2 units
Area of rectangle length x width
Area of square (length of a side)2
3
Lesson 8.BPage 2
Area ofRectangles and Squares
In algebra we use formulas to find the areas of
geometric shapes. The following formulas are
used for finding the areas of rectangles and
squares. Commit these to memory.
Area of a Rectangle
Area of a Square
4
Lesson 8.BPage 3
Area ofRectangles and Squares
Let us use the formulas to find the area of the
figures below.
6 units
3 units
3 units
3 units
5
Example 8.1
Area ofRectangles and Squares
Find the area of this figure. All angles are
right angles. Dimensions are in centimeters.
Use formulas.
2
4
A1
5
2
A2
6
Example 8.2
Area ofRectangles and Squares
Find the area of the shaded portion of this
figure. All angles are right angles. Dimensions
are in meters.
Use formulas.
6
2
8
A2
10
7
Lesson 8.3
Area ofTriangles
The altitude, or height, of a triangle is the
perpendicular distance from either the base of
the triangle or an extension of the base to the
opposite vertex.
h
h
h
b
Area of a Triangle
Commit this formula to memory.
8
Example 8.3
Area of Triangles
Find the area of these triangles. Dimensions are
in inches.
in2
9
Example 8.4
Area of Triangles
Find the area of this right triangle. Dimensions
are in feet.
8
6
10
ft2
10
Example 8.5
Area of Triangles
Find the area of this figure. Corners that look
square are square. Dimensions are in yards.
6
A1
4
A2
(6)
(4)
10
11
Example 8.6
Area of Circles
The radius of a circle is 3 centimeters. Find
the area of the circle.
Commit this formula to memory.
cm2
12
Example 8.7
Area of Circles
The area of a circle is 25 square meters. Find
13
Example 8.8
Area of Circles
Find the area of this figure. Lines that look
parallel are parallel. Dimensions are in inches.
Area area of triangle area of rectangle
area of semicircle
5
2
4
2
5
7
( )
in
14
Example 8.9
Area of Parallelogramsand Trapezoids
Find the area of this figure. Lines that look
parallel are parallel. Dimensions are in inches.
? Commit this formula to memory.
15
Example 8.10
Area of Parallelogramsand Trapezoids
Find the area of this trapezoid. Dimensions are
in meters.
Commit this formula to memory.
9
5
5
5
15
16
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