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11.2 areas of trapezoids, rhombuses, and kites
1. Sec. 10 – 2 Areas of Trapezoids and Kites Objectives: 1) Find the area of trapezoids. 2) Find the area of kites.
2. Trapezoids: leg leg b 1 = base 1 b 2 = base 2 h = height Height – distance between the 2 bases. * Must be A = ½ h(b 1 + b 2 ) Area of trapezoid Height base base
3. Ex. 1 Find the area of the following trapezoid. 20in 18in 36in 30in A = ½ h(b 1 + b 2 ) = ½ (18in)(36in + 20in) = ½ (18in)(56in) = 504in 2 This is the height!!
4. Ex. 2 Find the area of following trapezoid. 60 5cm 7cm A = ½ h(b 1 + b 2 ) = ½ (3.5cm)(5cm + 7cm) = ½ (3.5cm)(12cm) = 20.8cm 2 Need to find h first! Short side = 2cm h = 2 √ 3 h = 3.5cm This is a 30-60-90 Δ h
5.
6. Example 3: Find the Area of the following Kite. 3m 3m 4m 5m A = ½ d 1 d 2 = ½ (6m)(9m) =27m 2
7. Example 4: Find the area of the following rhombus 12m 12m b A = ½ d 1 d 2 = ½ (24m)(18m) = 216m 2 d 1 = 24m d 2 = 18m a 2 + b 2 = c 2 12 2 + b 2 = 15 2 144 + b 2 = 225 b 2 = 81 b = 9 15m 15m
