College

Select the correct answer.

A triangle has one side of length 29 units and another of length 40 units. Determine the range in which the length of the third side must lie.

A. [tex] -11 \ < \ x \ < \ 69 [/tex]
B. [tex] 11 \leq x \leq 69 [/tex]
C. [tex] 11 \ < \ x \ < \ 69 [/tex]
D. [tex] -11 \leq x \leq 69 [/tex]

Answer :

Sure, we can determine the range of the third side of a triangle using the triangle inequality theorem. This theorem states that the sum of the lengths of any two sides of a triangle must be greater than the length of the third side. This leads to a few key inequalities based on a triangle with sides [tex]\(a\)[/tex], [tex]\(b\)[/tex], and [tex]\(c\)[/tex]:

1. [tex]\(a + b > c\)[/tex]
2. [tex]\(a + c > b\)[/tex]
3. [tex]\(b + c > a\)[/tex]

For our triangle, we have two known sides: 29 units and 40 units. We need to find the possible range for the third side, which we'll call [tex]\(x\)[/tex].

Using the inequalities:

1. [tex]\(29 + 40 > x \Rightarrow x < 69\)[/tex]
2. [tex]\(29 + x > 40 \Rightarrow x > 11\)[/tex]
3. [tex]\(40 + x > 29 \Rightarrow x > -11\)[/tex] (This inequality isn't useful in this case since [tex]\(x > 11\)[/tex] is a tighter constraint.)

The useful inequalities are:
- [tex]\(x < 69\)[/tex] from the first inequality.
- [tex]\(x > 11\)[/tex] from the second inequality.

Therefore, by combining these, the length of the third side must lie in the range [tex]\(11 < x < 69\)[/tex].

The correct answer is:
C. [tex]\(11 < x < 69\)[/tex]