Answer:
The length of the longest side are all real numbers greater than 39 inches and less than 51 inches
Step-by-step explanation:
we know that
In an obtuse triangle
[tex]c^{2} >a^{2}+b^{2}[/tex]
where
c is the length of the longest side
a and b are the two shorter sides
Convert the dimensions in inches
[tex]1\ ft=12\ in[/tex]
[tex]3\ ft=3*12=36\ in[/tex]
substitute the values
[tex]c^{2} >15^{2}+36^{2}[/tex]
[tex]c^{2} >1,521[/tex]
[tex]c >39 in[/tex]
Applying the triangle inequality Theorem
1) [tex]15+36 >c[/tex]
[tex]c <51 in[/tex]
2) [tex]c+15 >36[/tex]
[tex]c>21 in[/tex]
therefore
The length of the longest side belong to the interval [tex](39,51)[/tex]
All real numbers greater than 39 inches and less than 51 inches