Answer: Option (4)
Step-by-step explanation:
From the diagram, we know that
[tex]\sin 60^{\circ}=\frac{BC}{15}\\\\\cos 60^{\circ}=\frac{AB}{15}[/tex]
This means we can eliminate options 1 and 2.
Now, if we multiply both sides by 15, we get
[tex]15\cos 60^{\circ}=7.5[/tex].
This gives us Option (4).
