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.

SECTION 11.3 AREAS of TRAPEZOIDS

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

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

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

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

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

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

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

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