Method 1 (easier method): Compute area of isosceles triangle BDE, add 4 of them plus the rectangles:
- Determine the length of segment S, using the pythagorean theorem:
S = ________________
- Compute area of triangle BDE
= _______
- 4 of these triangles = ______
- Determine area of rectangle CDEH =
= ___________
- Total all parts:
= ____________ sq. cm.
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Method 2: Cut into trapezoids and add up the parts.
- Determine the length of segment S
(see Method 1)
= ___________
- The length of line AB = ____________
- The area of trapezoid ABDC is
___________________
- 2 trapezoids =
____________
- 2 trapezoids + rectangle
(the whole octagon) =
_______________________
- Substituting our values for AB and S:
= _________________
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Method 3: (possibly cheating!): Use the equation for the area of a regular octagon:
A = 2 (1 + √
2) s2
s = 1 cm, so the area is:
________________ sq. cm.
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