Step-by-step explanation:
since in a triangle each side must be shorter than the sum of the other 2 sides (otherwise the end points cannot connect, and there is no triangle), the necessary inequality condition must be
side < 1 + 2 = 3
so,
side < 3
for a lower limit let's go through the cases
1 < 2 + side (is always true)
2 < 1 + side
1 < side (side must be larger than 1)
and again
side < 1 + 2 = 3
side < 3
so the full restriction for the third side is
1 < side < 3
