Answer:
D
Step-by-step explanation:
Using the cosine ratio and the exact value
cos45° = [tex]\frac{\sqrt{2} }{2}[/tex] , then
cos45° = [tex]\frac{adjacent}{hypotenuse}[/tex] = [tex]\frac{BC}{AC}[/tex] = [tex]\frac{BC}{n}[/tex] = [tex]\frac{\sqrt{2} }{2}[/tex] ( cross- multiply )
2BC = n[tex]\sqrt{2}[/tex] ( divide both sides by 2 )
BC = [tex]\frac{n\sqrt{2} }{2}[/tex] → D
