11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
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11­6 Surface Area and Volume of Spheres
1
11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
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Write down which homework problems you would like to go over from chapter 11. 2
11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
How are WE going to find the surface area of a sphere?
I could slice this sphere into many circles. A sphere is made up of circles stacked on top of each other.
3
11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
We ALREADY know the circumference of one circle...
d
4
11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
So, the SURFACE AREA
of the sphere is:
SA = Circumference of one circle x number of circles
SA = 4 r
2
sphere
5
11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
Try an example:
Find the surface area of a sphere that has a radius
of 5 inches.
Step 1: Start with the formula
5 in.
Step 2: Plug in the numbers
6
11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
Find the surface area of a sphere with a diameter of 8m. Leave your answer in terms of π.
7
11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
A sphere can be cut
into many small
pyramids.
If we can find the volume of
all these pyramids, we would
have the volume of the
sphere.
8
11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
The volume of a pyramid is:
V = A x h
base
3
So let's find the area of all the bases of the pyramids together.
So, what is the height of all the pyramids?
9
11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
V = A x h
base
3
V = SA of sphere x r
3
2
V = 4 r x r
3
4 3
V = r 3
10
11­6 Surface Area and Volume of Spheres 2011
Try one!
April 05, 2011
Find the volume of a sphere with radius 6 cm.
Step 1: Start with the formula
Step 2: Plug in the numbers
11
11­6 Surface Area and Volume of Spheres 2011
April 05, 2011
HOMEWORK
p. 640
(1-2, 5-6, 8-9, 14-18)
HOMEWORK
12