Question

An acute angle θ is in a right triangle with cos θ = 9/10 . What is the value of sec θ?

Answer 1

By definition

... sec(θ) = 1/cos(θ) . . . . trig identity

... sec(θ) = 1/(9/10) . . . . substitute the given value, then simplify to ...

... sec(θ) = 10/9

Answer 2

10/9 because sec x=1/cos x