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#1 2010-02-28 14:46:16
- waven
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- Registered: 2009-10-06
- Posts: 11
Surface Area of prisms, im lost :(
Calculate the surface area of the following prism.
i tried this serveral times,which all the answers were higher than the answer from the back of the book, which is
Thanks
Last edited by waven (2010-02-28 14:48:26)
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#2 2010-03-01 06:11:38
- mathsyperson
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- Registered: 2005-06-22
- Posts: 4,900
Re: Surface Area of prisms, im lost :(
The surface area is made up of two 'curvy triangles' and one 'curvy triangular tube'.
The area of the tube is easy enough once you've found the perimeter of the triangular shape.
The area of the triangle itself is a little harder.
I'd do it by first working out what its area would be if you cut off the left hand segment (ignoring the part to the left of line AC), then working out what it would be if you cut off both segments (making it a proper triangle).
By combining those two results in some way, you can find the area of the whole shape.
Edit: I've just done it and got ~8306, so maybe the book's wrong. (But I easily could be too. 
)
Why did the vector cross the road?
It wanted to be normal.
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#3 2010-03-01 08:45:49
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: Surface Area of prisms, im lost :(
Hi waven;
What book?
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#4 2010-03-01 08:57:33
- waven
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- Registered: 2009-10-06
- Posts: 11
Re: Surface Area of prisms, im lost :(
Hi waven;
What book?
hi, the book is signpost maths yr9 5.3
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#5 2010-03-01 09:16:36
- waven
- Member
- Registered: 2009-10-06
- Posts: 11
Re: Surface Area of prisms, im lost :(
The surface area is made up of two 'curvy triangles' and one 'curvy triangular tube'.
The area of the tube is easy enough once you've found the perimeter of the triangular shape.
The area of the triangle itself is a little harder.I'd do it by first working out what its area would be if you cut off the left hand segment (ignoring the part to the left of line AC), then working out what it would be if you cut off both segments (making it a proper triangle).
By combining those two results in some way, you can find the area of the whole shape.
yeah i tried that before but the answer's
, im not sure if this is correct but my ABC is is this correct?edit: this is what i did for ABC whilst ignoring AC
Last edited by waven (2010-03-01 09:32:44)
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#6 2010-03-03 09:06:43
- White_Owl
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- Registered: 2010-03-03
- Posts: 106
Re: Surface Area of prisms, im lost :(
Yes, the area of the ABC sector is
So the full area of the rounded triangle should be a sum of two sectors minus area of normal equilateral triangle:
Length of the arc BC (or AC):
So the whole surface of this 'curvy triangle tube' should be:
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