Answer:
9.271 inches.
Step-by-step explanation:
Let AC be the length of original line segment and point B divides it into two segments such that AB is longer and BC is smaller segment.
[tex]AB+BC=AC=15[/tex]
We can describe the golden ratio as:
[tex]\frac{AB}{BC}=\frac{AC}{AB}=1.618[/tex]
[tex]\frac{AC}{AB}=1.618[/tex]
[tex]\frac{15}{AB}=1.618[/tex]
[tex]\frac{15}{1.618}=AB[/tex]
[tex]9.270704=AB[/tex]
[tex]AB=9.271[/tex]
We can verify our answer as:
[tex]AB+BC=15[/tex]
[tex]9.271+BC=15[/tex]
[tex]9.271-9.271+BC=15-9.271[/tex]
[tex]BC=5.729[/tex]
[tex]\frac{AB}{BC}=1.618[/tex]
[tex]\frac{9.271}{5.729}=1.618[/tex]
[tex]1.618=1.618[/tex]
Hence proved.
Therefore, the length of the longer side would be 9.271 inches.