Answer:
[tex]\large\boxed{x\approx12.94}[/tex]
Step-by-step explanation:
Use cosine:
[tex]\cosine=\dfrac{adjacent}{hypotenuse}[/tex]
We have:
[tex]adjacent=4\\hypotenusex\\\alpha=72^o\\\\\cos72^o\approx0.309[/tex]
Substitute:
[tex]\dfrac{4}{x}=0.309[/tex]
[tex]\dfrac{4}{x}=\dfrac{309}{1000}[/tex] cross multiply
[tex]309x=4000[/tex] divide both sides by 309
[tex]x\approx12.94[/tex]
