1. ## Triangle

To prove that sum of two sides of a triangle minus the third side is less than the third side?

2. let the sides be $\displaystyle a,b,c$ so you have to prove $\displaystyle a+b-c<c$

Keep in mind $\displaystyle a+b>c$

3. ?

4. Originally Posted by soni
but how i can prove that a + b > c ?
That is a given otherwise you would not have a triangle.

5. will you give me proof of this question i.e. a + b - c < c ?

6. Let's re-write it like this

$\displaystyle a + b - c < c$

$\displaystyle c> a + b - c$

and because $\displaystyle a+b>c$ then it still holds that

$\displaystyle a+b> a + b - c$

now given $\displaystyle a,b, c>0$ then we must be finished!

7. Thanks a lot