Answer:
4.5 m
Step-by-step explanation:
Distance from center to the the bottom part where headroom begins is 3.9 m-2.6 m=1.3 m
Since the radius is 2.6 m and acts as hypotenuse(see attached image), then the other length will be
[tex]\sqrt {2.6^{2}-1.3^{2}=5.07}=2.25166605
[/tex]
Approximately 2.25 m
The half width is 2.25 m hence full width will be 2.25*2=4.5 m
