1. Section 11-5: Areas of Triangles & Trapezoids
Pg.558

2. Objective & Vocabulary
Find the areas of triangles and trapezoids.
Triangles
Base of a triangle (pg.558): the length of any one of the sides.
Height of a triangle (pg.558): the perpendicular distance between the base and the vertex opposite that side.
Area of a triangle (pg.558): The product of ½ the base and height (A= ½ bh).
Height h
Height h
Base b
Base b

3. Example 1: Finding the Area of a Triangle
Find the area of the following triangle.
Find the area if the base is 9in and the height is 6in.

4. Example2: Finding the Base/Height of a Triangle
A triangle has a height of 10 cm and an area of 35 sq. cm. Find the base of the triangle.
Find the height of a triangle if the base is 11 m and the area is 61.6 sq. m.

5. Trapezoids
Bases of a trapezoid (pg.559): the lengths of the parallel sides of a trapezoid.
Height of a trapezoid (pg.559): the perpendicular distance between the bases.
Area of a trapezoid (pg.559): half the product of the sum of the bases and the height [A= ½ (b1 + b2)h].
Base b1
Base b1
Height h
Height h
Base b2
Base b2

6. Example 3: Finding the Area of a Trapezoid
Find the area of the trapezoid shown.
Find the area of a trapezoid if the bases are 13 in and 15 in, and the height is 6 in.

7. Homework Time—Yea!!
Pg (1-15all, 22-25all)