You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

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'

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

Offline

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,071

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

Offline

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'

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

Offline

**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,037

You can do it like this:

CD<AC+AD<(AB+BC)+AD. Q.E.D

*Last edited by anonimnystefy (2012-11-05 01:40:45)*

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

Offline

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'

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

Offline

**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,037

You are welcome!

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

Offline

Pages: **1**