The base of a triangle is the length of any of its sides. The height of a triangle is the perpendicular distance between the side whose length is the base and the vertex opposite that side.
NOTE BOOK
Words
Algebra
Area of a Triangle
A = bh12
Area of a triangle = • base • height12
h
b
Area of a Triangle10 2.
Finding the Area of a TriangleEXAMPLE 1
Find the area of the triangle shown.
11 ft
4 ft
A = bh12
Write the formula for the
area of a triangle.
Substitute 4 for b and 11 for h.
Simplify.
= bh12
= 22
ANSWER The area of the triangle is 22 square feet.
Area of a Triangle10 2.
• 4 • 11
Finding the Area of Combined FiguresEXAMPLE 2
Tall Ships A pattern of a sail for a tall ship is shown. How much material, in square feet, is needed to make the sail?
Find the area of each shape.
A = 6
ANSWER You will need 30 square feet of material to make the sail.
4 ft
6 ft
3 ftSOLUTION
1
2
Area of the triangle: Area of the rectangle:
A = • 4 • 312
A = 4 • 6
A = 24
Add the areas together to find the total area.
6 + 24 = 30
Area of a Triangle10 2.
A = • b • h12
Finding the Height of a TriangleEXAMPLE 3
The area of a triangle is 36 square inches and the base is 8 inches. What is the height of the triangle?
A = bh12
Write the formula for the area of a
triangle.
36 = 4 • h
Substitute 36 for A and 8 for b.
h = 36 4
Simplify.
Write a related division equation.
h = 9 Simplify.
ANSWER The height of the triangle is 9 inches.
Area of a Triangle10 2.
36 8