# Math Help - Triangle

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 $a,b,c$ so you have to prove $a+b-c

Keep in mind $a+b>c$

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

$a + b - c < c$

$c> a + b - c$

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

$a+b> a + b - c$

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

7. Thanks a lot