Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**thedarktiger****Member**- Registered: 2014-01-10
- Posts: 91

In the triangle shown, n is a positive integer, and \angle A > \angle B > \angle C. How many possible values of n are there?

theres a figure but im new so I cant post wahh

The sides are AB = 4n-9, BC = 3n+4, AC = 3n+1.

I figured out BC is the biggest and AC is second and AB is third biggest. pls help. thx a ton!!!!!:D

Good. You can read.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,548

hi thedarktiger,

In any triangle with sides p, q and r

p + q > r

If you use this three times, taking a different side as r each time, then you will get inequalities involving n.

Also, the minus in the expression for AB leads to a fourth inequality.

All must be true so pick the most limiting which will give a lower bound.

Then you have the inequalities on the sides which will give an upper bound.

Bob

*Last edited by bob bundy (2014-01-15 21:08:47)*

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

Offline

**thedarktiger****Member**- Registered: 2014-01-10
- Posts: 91

Oh thanks Im so stupid I thought something was wrong with the problem! Thx so much

Good. You can read.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,548

Oh that's not so stupid. I worked out the triangle inequality results and totally forgot the BC > AC > AB ones. It was only when I looked at your quadrilateral post that it occurred to me that I'd left out half the information.

As for the quad problem:

It's a tough one if the points make a random quad. But once you realise three points are in a straight line it becomes easier. So maybe that was deliberate?

Taking the two problems together it looks like the book is testing the triangle inequality in both so it begins to make sense.

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

Offline

Pages: **1**