Area and Properties of Octagons

Area and Properties of Octagons

Assessment

Interactive Video

Mathematics

9th - 10th Grade

Hard

Created by

Thomas White

FREE Resource

The video tutorial explains how to calculate the area of a regular octagon given a side length. It starts by discussing the challenges of using the traditional formula involving the apothem and perimeter. Instead, the tutorial introduces a creative method using diagonals to form trapezoids and a rectangle, which simplifies the calculation. The process is detailed step-by-step, and a general formula is derived for any side length. The tutorial emphasizes the importance of the 45-45-90 triangle in solving the problem.

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9 questions

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1.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is the initial side length given for the octagon in the problem?

3

4

5

6

2.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Why is the standard formula for the area of a regular polygon not applicable in this problem?

The perimeter is not given

The side length is unknown

The formula is incorrect

The apothem is difficult to find

3.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What shapes are created by drawing diagonals in the octagon?

Two triangles and a square

Two trapezoids and a rectangle

Two rectangles and a triangle

Two squares and a triangle

4.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What type of triangle is used to find the altitude of the trapezoid?

60-60-60 triangle

45-45-90 triangle

30-60-90 triangle

30-30-120 triangle

5.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

How is the altitude of the trapezoid calculated using the 45-45-90 triangle?

By multiplying the side length by √2

By dividing the side length by √2

By adding the side length to √2

By subtracting the side length from √2

6.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is the area of one trapezoid in the octagon?

12 + 12√2

16 + 16√2

8 + 8√2

4 + 4√2

7.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is the total area of the octagon when the areas of the trapezoids and rectangle are summed?

16 + 16√2

32 + 32√2

24 + 24√2

40 + 40√2

8.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What variable is used to generalize the side length in the formula?

X

Z

Y

W

9.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is the final generalized formula for the area of a regular octagon?

3x^2 + 3x^2√2

4x^2 + 4x^2√2

x^2 + x^2√2

2x^2 + 2x^2√2