Answer:

Explanation:
For the first one, in any triangle, we have the sum of two sides is greater than the third side. Hence, we have 3 inequalities: 
 , which give us
, which give us 
 . We conclude that
. We conclude that 
 .
.
For the second question, we have 
 , and similarly we can show that
, and similarly we can show that 
 . Hence,
. Hence, 
 .
.
The third question is not very clear.