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#1 2012-09-07 21:03:01

Agnishom
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A few simple proofs about Triangles

Let there be a triangle ABC and O a point inside it.
Now, how can I prove that:
1.


2.

Last edited by Agnishom (2012-09-07 21:04:17)


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#2 2012-09-07 22:59:19

bob bundy
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Registered: 2010-06-20
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Re: A few simple proofs about Triangles

hi Agnishom

Here's a start for number 2.

AO + OB > AB

Bob

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You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#3 2012-09-08 00:15:42

Agnishom
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From: The Complex Plane
Registered: 2011-01-29
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Re: A few simple proofs about Triangles

I did 2.



Adding all those,


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#4 2012-09-08 00:28:22

bob bundy
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Registered: 2010-06-20
Posts: 6,469

Re: A few simple proofs about Triangles

Excellent!

I am hoping there's a similar way to do Q1 but, so far, it has eluded me.

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#5 2012-09-08 00:37:29

Agnishom
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From: The Complex Plane
Registered: 2011-01-29
Posts: 18,129
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Re: A few simple proofs about Triangles

I remember doing it at the 7th Grade, but what about 1.?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#6 2012-09-08 01:27:25

noemi
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Registered: 2010-01-07
Posts: 2,333

Re: A few simple proofs about Triangles

Hint for 1.:
OA+OB<CA+CB

Last edited by noemi (2012-09-08 01:29:34)

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#7 2012-09-08 03:55:11

Agnishom
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From: The Complex Plane
Registered: 2011-01-29
Posts: 18,129
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Re: A few simple proofs about Triangles

noemi wrote:

Hint for 1.:
OA+OB<CA+CB

Why?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#8 2012-09-08 03:56:12

Agnishom
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From: The Complex Plane
Registered: 2011-01-29
Posts: 18,129
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Re: A few simple proofs about Triangles

Please somebody help me!


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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#9 2012-09-08 04:23:50

noemi
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Registered: 2010-01-07
Posts: 2,333

Re: A few simple proofs about Triangles

OA+OB<CA+CB
OB+OC<AB+AC
OC+OA<BC+BA

adding all those you get what you need, assuming CA=AC etc.

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#10 2012-09-08 13:59:03

Agnishom
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From: The Complex Plane
Registered: 2011-01-29
Posts: 18,129
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Re: A few simple proofs about Triangles

Hmmmmmm..................
That set of problem had another problem which I shall be posting in a new thread


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'You have made another human being happy. There is no greater accomplishment.' -bobbym

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