Areas of Trapezoids, Rhombuses, and Kites

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Section 7-4

• Areas of Trapezoids, Rhombuses, and Kites

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Theorem 7-10Area of a Trapezoid

• The area of a trapezoid is one-half the product
  of the height and the sum of the bases
• A½h(b1 b2)

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Example Find the Area
21 in
16 in
38 in
A ½ (h)(b1 b2)
A ½ (16)(21 38)
A (8)(59)
A 472 in²
4
Find the area of the Trapezoid
Area 144 sq. units
5
Find Area using triangle rules
M
11
X 8/2 4
8 ft
Y
4v3
M 15 4 11
60?
X
15 ft
4
Y 4v3
A ½ (4v3) (11 15)
A (2v3) (26)
A 52v3 ft²
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Theorem 7-11Area of a Rhombus or a Kite

• The area of a rhombus or a kite is one-half the
  product of the lengths of its diagonals.
• A½(d1)(d2)

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Find the area of the Rhombus

• d1 12
• d2 9

A ½ (d1)(d2) A ½ (12)(9) A 54 sq. units
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Find Area of Rhombus
A ½ (d1)(d2)
A ½ (18 m)( 24 m)
A 216 m²
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Find the Area
We need to find the length of the other diagonal
9m
BEC is a Right Triangle
Using the Pythagorean triple, BE 9 m
A ½ (d1)(d2)
A ½ (18 m)(24 m) 216 m²
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Assignment

• Page 376
• 1-4, 8-20even, 29-31