# Lesson 9-1: Area of 2-D Shapes 1 Lesson 9-1 Area of 2-D Shapes.

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Lesson 9-1: Area of 2-D Shapes 1 Lesson 9-1 Area of 2-D Shapes

Lesson 9-1: Area of 2-D Shapes 2 Squares and Rectangles s s A = s² 6 6 A = 6² = 36 sq. units L W A = LW 12 5 A = 12 x 5 = 60 sq. units Example: Area of Rectangle: A = LW Area of Square: A = s²

Lesson 9-1: Area of 2-D Shapes 3 Circles and Sectors r 9 cm A =  (9)² = 81  sq. cm Area of Circle: A =  r² arc r B C A 120° Example: 9 cm

Lesson 9-1: Area of 2-D Shapes 4 Triangles and Trapezoids h h h bb b1b1 b2b2 h is the distance from a vertex of the triangle perpendicular to the opposite side. h is the distance from b1 to b2, perpendicular to each base

Lesson 9-1: Area of 2-D Shapes 5 Example: Triangles and Trapezoids 7 6 8 12 6

Lesson 9-1: Area of 2-D Shapes 6 Parallelograms & Rhombi Area of Parallelogram: A = b h 6 9 A = 9 x 6 = 54 sq. units 8 10 A = ½ (8)(10) = 40 sq units h b Example:

Lesson 9-1: Area of 2-D Shapes 7 Area of Regions 8 10 12 414 8 The area of a region is the sum of all of its non-overlapping parts. A = ½(8)(10) A= 40 A = (12)(10) A= 120 A = (4)(8) A=32 A = (14)(8) A=112 Area = 40 + 120 + 32 + 112 = 304 sq. units

Lesson 9-1: Area of 2-D Shapes 8 Areas of Regular Polygons Perimeter = (6)(8) = 48 apothem = Area = ½ (48)( ) = sq. units 8 If a regular polygon has an area of A square units, a perimeter of P units, and an apothem of a units, then A = ½ (a)(p).

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