SA of Pyramids and Cones 2010 May 03, 2010
Sep 226:57 PM
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SA of Pyramids and Cones 2010
To find the surface area of a pyramid, first make a "net".
Pyramid with
Square base unfold to get
Net
May 03, 2010
Sep 227:02 PM
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SA of Pyramids and Cones 2010 May 03, 2010 face face base face face
To find the surface area of a pyramid, find the area of its base and then add the area of its faces.
SA = Area of Base + Area of Faces
Sep 227:15 PM
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SA of Pyramids and Cones 2010
4 ft.
Find the surface area of this pyramid.
First, label the net.
6 ft.
6 ft.
6 ft.
6 ft.
6 ft.
How are we going to find the height of the triangles?
May 03, 2010
Sep 227:37 PM
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SA of Pyramids and Cones 2010 May 03, 2010
4 ft.
6 ft.
Use the Pythagorean Theorem to find the length.
2 a + b = c 2
2 2
3 + 4 = c 2
9 + 16 = c 2
25 = c 2
25 = c 2
5 = c
Sep 227:54 PM
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SA of Pyramids and Cones 2010 May 03, 2010
4 ft.
5
6 ft.
5
6 ft.
5
6 ft.
6 ft.
5
6 ft.
5
Sep 228:15 PM
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SA of Pyramids and Cones 2010 May 03, 2010
5
6 ft.
5
6 ft.
6 ft.
5
6 ft.
5
1. Find the Area of the Base
6(6) = 36
2. Find the Area of the Faces
A = 1/2 b h
= 1/2 (6)(5)
= 15
3. Add them together to get the Surface Area
SA = Base + 4 Faces
= 36 + 4(15)
= 36 + 60
= 96 square feet
Sep 228:18 PM
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SA of Pyramids and Cones 2010 May 03, 2010
To find the surface area of a cone, first make a "net".
s
NET r
Feb 215:47 AM
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SA of Pyramids and Cones 2010 May 03, 2010
Feb 215:53 AM
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SA of Pyramids and Cones 2010 May 03, 2010 r s Find the area of each piece and then add them together.
Area of the Circle:
A = r
2
Feb 215:53 AM
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SA of Pyramids and Cones 2010 May 03, 2010 r s
Area of the sector:
First, cut the sector into many triangles .
Feb 215:54 AM
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SA of Pyramids and Cones 2010 May 03, 2010 r s
Area of the sector:
First, cut the sector into many triangles .
If we find the area of the triangles, we will have the area of the sector!
Feb 215:55 AM
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SA of Pyramids and Cones 2010 May 03, 2010 s
Area of the sector:
First, cut the sector into many triangles .
If we find the area of the triangles, we will have the area of the sector!
r
A = b h
2
The base of ALL the triangles together is the Circumference of the circle!
The height of all the triangles is s.
Feb 215:55 AM
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SA of Pyramids and Cones 2010 May 03, 2010 s
Area of the sector:
First, cut the sector into many triangles .
If we find the area of the triangles, we will have the area of the sector!
r
A = b h
2
The base of ALL the triangles together is the Circumference of the circle!
A = C s
2
The height of all the triangles is s.
C = 2 r
A = 2 rs
2
Area of the Sector A = rs
Feb 215:55 AM
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SA of Pyramids and Cones 2010 May 03, 2010 s
Now, add the two areas together!
A = r
2
+ rs r
A = r
2
A = rs
Factor out a common term:
A = r(r + s)
Feb 215:56 AM
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SA of Pyramids and Cones 2010 May 03, 2010
The surface area of a cone is:
Feb 215:57 AM
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SA of Pyramids and Cones 2010 May 03, 2010
Let's try one! Find the surface area of this cone.
Step 1: Find "s".
Step 2: Use the formula to find the surface area.
SA = r(r + s) h = 5 in.
r = 2 in.
Feb 215:58 AM
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SA of Pyramids and Cones 2010
May 03, 2010
Sep 228:22 PM
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