### Theory:

In any triangle, the sum of the length of any two sides is always greater than the length of the third side.

Here $$AB = c, BC = a$$ and $$CA = b$$.

Thus the above inequality can be written in the notations as follows:

$$a + b > c$$

$$b + c > a$$ and

$$c + a > b$$.

Example:
Consider the triangle $$ABC$$ with sides measures $$AB = c = 3 cm, BC = a = 4 cm$$ and $$AC = b = 5 cm$$.

Let's check the triangle inequality for the triangle $$ABC$$,

$$a + b = 4 + 5 = 9 > 3 = c$$

$$b + c = 5 + 3 = 8 > 4 = a$$ and

$$c + a = 3 + 4 = 7 > 5 = b$$.