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

Agnishom
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From: Riemann Sphere
Registered: 2011-01-29
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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'
I'm not crazy, my mother had me tested.

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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

Children are not defined by school ...........The Fonz
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: Riemann Sphere
Registered: 2011-01-29
Posts: 24,442
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### Re: A few simple proofs about Triangles

I did 2.

'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'
I'm not crazy, my mother had me tested.

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

bob bundy
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Registered: 2010-06-20
Posts: 7,743

### 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

Children are not defined by school ...........The Fonz
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: Riemann Sphere
Registered: 2011-01-29
Posts: 24,442
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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'
I'm not crazy, my mother had me tested.

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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: Riemann Sphere
Registered: 2011-01-29
Posts: 24,442
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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'
I'm not crazy, my mother had me tested.

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

Agnishom
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From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,442
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### Re: A few simple proofs about Triangles

'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'
I'm not crazy, my mother had me tested.

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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: Riemann Sphere
Registered: 2011-01-29
Posts: 24,442
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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'
I'm not crazy, my mother had me tested.

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