Geometry Handout

# Geometry Handout - Geometry Perimeter: Perimeter is defined...

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Geometry Perimeter : Perimeter is defined as the distance around an object. For a polygon (an object with many sides) the perimeter is the sum of the lengths of the sides. For a circle the distance around the outside is called the circumference. Rectangle Square Triangle Circle P = 2 l + 2w P = 4s P = a + b + c Circumference: C = 2 π r Example 1: Finding Perimeter and Circumference Find the perimeter or circumference as indicated. Use 3.14 for π . a. Perimeter: b. Perimeter: c. Circumference Solution : a. P = a + b + c P = 4 in. + 2 in. + 5 in. Add the lengths of the sides = 11 in. The perimeter is 11 inches b. P = 2 l + 2w P = 2(5.5 ft) + 2(3.1 ft) Substitute l = 5.5 ft and w = 3.1 ft = 11 ft + 6.2 ft = 17.2 ft The perimeter is 17.2 feet

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c. C = 2 π r C = 2( π )(6 cm) Substitute r = 6 cm and leave π in your answer. = 12 π cm The circumference is 12 π cm Area : The area of an object is the number of square units that can be enclosed within the figure. For example, the rectangle to the right encloses 6 square inches (6 in 2 ). Rectangle Square Parallelogram A = l w A = s 2 A = bh Triangle Trapezoid Circle A = 1 2 bh A = 1 2 12 () bb h + A = π r 2 Example 2: Finding Area Find the area enclosed by each figure. a . b .
Solution : a. A = bh The figure is a parallelogram A = () 42 1 4 1 2 in in Substitute b = 4 1 4 in. and h = 2 1 2 in. = 17 4 5 2 in in = 85 8 2 or 10 5 8 2 b. A = 1 2 12 bb h + The figure is a trapezoid A = 1 2 16 10 3 ( ) yds + Substitute b 1 = 16 yds, b 2 = 10 yds, and h = 3 yds = ) yds 3 )( yds 26 ( 2 1 = (13 yds)(3 yds) = 39 yds 2 The area is 39 yds 2 Example 3: Finding Area of a Circle Find the area of a circular fountain if the radius is 25 feet.

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## This note was uploaded on 05/12/2011 for the course TED 455 taught by Professor Espisito during the Spring '11 term at CSU Dominguez Hills.

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Geometry Handout - Geometry Perimeter: Perimeter is defined...

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