Answer:
b = 4
Step-by-step explanation:
Using the trigonometric identity
cos x = [tex]\frac{1}{secx}[/tex] = [tex]\frac{1}{\frac{5}{3} }[/tex] = [tex]\frac{3}{5}[/tex]
Using the cosine ratio in the right triangle
cos x = [tex]\frac{adjacent}{hypotenuse}[/tex] = [tex]\frac{3b}{20}[/tex]
Hence
[tex]\frac{3b}{20}[/tex] = [tex]\frac{3}{5}[/tex] ( cross- multiply )
15b = 60 ( divide both sides by 15 )
b = 4
