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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 made a human being happy! There is no further achievement.' -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
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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 made a human being happy! There is no further achievement.' -bobbym

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

bob bundy
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Registered: 2010-06-20
Posts: 6,418

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: 17,124
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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 made a human being happy! There is no further achievement.' -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: 17,124
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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 made a human being happy! There is no further achievement.' -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: 17,124
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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 made a human being happy! There is no further achievement.' -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: 17,124
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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 made a human being happy! There is no further achievement.' -bobbym

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