Geometry Chapter 1 - Essentials of Geometry Section 1.7 - Find perimeter, circumference, and area What the student should get from this: 1. Apply formulas for perimeter, area, and circumference What is perimeter?
What is the perimeter of the figure at the right? (assume right angles) 26 ft
46 ft For rectangular figures p = 2l + 2w 14.3 ft Example: 5.8 ft
For triangular figures... add up the sides.!!
6 cm !
6 5cm For circles, use C = 2! r or C = ! d Example: 15 cm
Another Example: What is the radius of the circle with circumference of 15 cm?
Let始s talk area! The formula for the area of a rectangle is A = bh or area equals base times height. Example:
7 3 ft
12 7 ft There are several area formulas for triangles... (Memorize them!)
1 bh 2
s2 3 4
for equilateral triangles only
Example: to use this formula, you must know the length of the base and the height of the triangle
height always makes a right angle with the base
Find the perimeter of each figure: 10 in. 6 in.
7 in. 9 in. 6 in.
Lastly, the area of a circle is given by A = ! r 2 . Examples: find the area of each...
circumference is 14Ď€
A couple more things: The area of a triangle is 282.5 sq. ft. The height is 22.6 ft. How long is the base?
The perimeter of a rectangular fountain is 120 3 ft . The base is 40 feet. How wide is the fountain?
The length of a rectangular flower bed is 3 times the width. The area is 300 square feet. What are the dimensions of the flower bed?
Assignment: p.52 #s 3-17 odd, 27-29 all, 32, 46, 47. Show work. Draw all pictures. Due next period.