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## #1 2012-11-06 00:07:11

Agnishom
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### Those inequalities again

Prove that in a quadrilateral ABCD,
AB + BC + CD > DA

'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'
'The whole person changes, why can't a habit?' -Alokananda

## #2 2012-11-06 00:14:37

bob bundy
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### Re: Those inequalities again

hi

Split your quadrilateral into two triangles and use the triangle inequality twice.

Bob

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

## #3 2012-11-06 00:25:36

Agnishom
Real Member

Online

### Re: Those inequalities again

Tried...But how do I get rid of the diagonal in the equation?

'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'
'The whole person changes, why can't a habit?' -Alokananda

## #4 2012-11-06 00:39:44

anonimnystefy
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### Re: Those inequalities again

You can do it like this:

Last edited by anonimnystefy (2012-11-06 00:40:45)

The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

## #5 2012-11-06 01:40:53

Agnishom
Real Member

Online

### Re: Those inequalities again

Yes! Thanks to bob bundy and anonimnystefy

'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'
'The whole person changes, why can't a habit?' -Alokananda

## #6 2012-11-06 01:43:35

anonimnystefy
Real Member

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### Re: Those inequalities again

You are welcome!

The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment