Question: A zip wire runs between two posts, 30m apart. The zip wire is at an angle of 60° to the horizontal. Calculate the length of the zip wire.
Solution: 
Given,
Horizontal distance between posts is 30 meters
Angle of elevation, θ = 60°
Then, we find the Length of the zip wire (hypotenuse) = L
Since we know the adjacent side and the angle, and we need to find the hypotenuse, we use the cosine function.
⇒ cos(θ) = Adjacent/Hypotenuse
⇒ cos(60°) = 30/L
⇒ L = 30/(1/2)
= 30 × 2
= 60 m
So, Length of zip wire is = 60 m