Area of Triangles and Trapezoids

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Area of Triangles and Trapezoids Course 2 9-4 Area of Triangles and Trapezoids AREA OF A TRIANGLE The area A of a triangle is half the product of its base b and its height h. 1 2 A = bh h b

Additional Example 1A: Finding the Area of a Triangle Course 2 9-4 Area of Triangles and Trapezoids Additional Example 1A: Finding the Area of a Triangle Find the area of the triangle. 1 2 A = bh Use the formula. 5 1 2 Substitute 8 for b and 5 for h. A = (8 · 5) 8 A = 20 The area of the triangle is 20 square units.

Additional Example 1B: Finding the Area of a Triangle Course 2 9-4 Area of Triangles and Trapezoids Additional Example 1B: Finding the Area of a Triangle Find the area of the triangle. 1 2 A = bh Use the formula. 12 1 2 A = (9 · 12) 9

Area of Triangles and Trapezoids Course 2 9-4 Area of Triangles and Trapezoids Check It Out: Example 1B Find the area of the triangle. 1 2 A = bh

Area of Triangles and Trapezoids Course 2 9-4 Area of Triangles and Trapezoids The two parallel sides of a trapezoid are its bases, b1 and b2. The height of a trapezoid is the perpendicular distance between the bases. b2 h b1

Area of Triangles and Trapezoids Course 2 9-4 Area of Triangles and Trapezoids AREA OF A TRAPEZOID b2 The area of a trapezoid is half its height multiplied by the sum of its two bases. 1 2 A = h(b1 + b2) h b1 In the term b1, the number 1 is called a subscript. It is read as “b-one” or “b sub-one.” Reading Math

Additional Example 2A: Finding the Area of a Trapezoid Course 2 9-4 Area of Triangles and Trapezoids Additional Example 2A: Finding the Area of a Trapezoid Find the area of the trapezoid. 5 in. 1 2 A = h(b1 + b2) Use the formula. 1 2 A = · 6(5 + 9) 6 in. Substitute. 1 2 A = · 6(14) Add. 9 in. A = 42 Multiply. The area of the trapezoid is 42 in2.

Area of Triangles and Trapezoids Course 2 9-4 Area of Triangles and Trapezoids Check It Out: Example 2A Find the area of the trapezoid. 1 2 A = h(b1 + b2) Use the formula. 1 2 A = · 6(11.2 + 4.3) Substitute. 11.2 in. 4.3 in. 6 in. Add. Multiply.

Additional Example 3: Geometry Application Course 2 9-4 Area of Triangles and Trapezoids Additional Example 3: Geometry Application The state of Wisconsin is shaped somewhat like a trapezoid. What is the approximate area of the state? 1 2 A = h(b1 + b2)