One example is if you wanted to measure the height of a tall building. You'll need to measure the distance from where you're standing to the base of the building. You'll also need the angle of elevation. To get the angle of elevation, start by looking completely horizontal, then tilt upward until your eyeline reaches the top of the building. Once you have those two things (the side and angle) you can use the tangent ratio to find the height. This is because
tan(angle) = opposite/adjacent
where in this case angle = angle of elevation opposite = height of building adjacent = distance from your position to the base of the building
It takes a bit of algebra, but the opposite side can be solved for. You'll most likely need a calculator to compute the tangent ratio.
