1. WARM UP Find the area of an equilateral triangle with sides 8 ft.
Find the area of a parallelogram with a 45 degree angle and sides 6 and 10.
Find the area of a rectangle with length 16 inscribed in a circle with radius 10.

2. SECTION 11.3
AREAS of TRAPEZOIDS

3. Trapezoid Review
Trapezoid: quadrilateral with one pair of opposite sides that are parallel.
Median: AVERAGE of the two bases
BASE
MEDIAN

4. A= ½ h(b1 + b2) Area of TRAPEZOIDS h = height (perpendicular height)
b1 = the first base
b2 = the second base 8 16 o
30o 4 8 4

5. A= ½ h(b1 + b2) A= ½ (5)(7 + 13) A= ½ (5)(20) A= ½ (100) A= 50
1) A trapezoid has bases 7 and 13 and a height of 5.
Find the area of the trapezoid.
Find the length of the median.
Median = average of the bases
A= ½ h(b1 + b2)
A= ½ (5)(7 + 13)
Median = (7 + 13) / 2
A= ½ (5)(20)
Median = 20 / 2
A= ½ (100)
Median = 10
A= 50

6. A= ½ h(b1 + b2) 75 = ½ (5)(b1 + b2) M = (b1 + b2) / 2
2) A trapezoid has an area of 75 cm2 and a height of 5 cm. How long is the median?
Median = average of the bases
A= ½ h(b1 + b2)
75 = ½ (5)(b1 + b2)
Plug in what you know
M = (b1 + b2) / 2
75 = (2.5)(b1 + b2)
Divide both sides by 2.5
M = 30 / 2
30 = (b1 + b2)
M = 15

7. A= ½ h(b1 + b2) A = ½ (12)(9 + 14) M = (14 + 9) / 2 A = ½ (12)(23)
3) Find the area of the trapezoid.
Find the length of the median.
A= ½ h(b1 + b2)
Median = average of the bases
A = ½ (12)(9 + 14)
M = (14 + 9) / 2
A = ½ (12)(23)
M = 23 / 2
A = 6(23)
M = 11.5
A = 138

8. SAT Problem
Find the area of a trapezoid with vertices at A(0,0), B(2,4), C(6,4), and D(9,0).
13 square units
18 square units
26 square units
36 square units
52 square units
A = ½ h(b1 + b2)
A = ½ 4(4 + 9)
A = ½ 4(13)
A = 26
A = 2(13)
A = 26 4 B C 4 A 9 D

9. Practice Problems Page 435 – 436 Classroom Exercises #1 - 3 and 8 – 10
Draw diagrams.

10. Area Video
Don’t you just love these videos!!!!