Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °
You are not logged in.
#1 2012-11-06 00:07:11
- Agnishom
- Star Member
Offline
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?' -65
#3 2012-11-06 00:25:36
- Agnishom
- Star Member
Offline
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?' -65
#4 2012-11-06 00:39:44
- anonimnystefy
- Real Member
Offline
Re: Those inequalities again
You can do it like this:
CD<AC+AD<(AB+BC)+AD. Q.E.D
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
“A secret's worth depends on the people from whom it must be kept.” ― Carlos Ruiz Zafón
#5 2012-11-06 01:40:53
- Agnishom
- Star Member
Offline
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?' -65
#6 2012-11-06 01:43:35
- anonimnystefy
- Real Member
Offline
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
“A secret's worth depends on the people from whom it must be kept.” ― Carlos Ruiz Zafón