Question

What is the correct value of b ?

Answer 1

b = 4

Explanation:

Using the trigonometric identity

cos x =
`(1)/(secx)` =
`(1)/((5)/(3) )` =
`(3)/(5)`

Using the cosine ratio in the right triangle

cos x =
`(adjacent)/(hypotenuse)` =
`(3b)/(20)`

Hence

`(3b)/(20)` =
`(3)/(5)` ( cross- multiply )

15b = 60 ( divide both sides by 15 )

b = 4