Solving Real World Problems Using the Law of Cosines Video Oct 20, 2014Real-World Uses. The beauty of the law of cosines can be seen when you want to find the location of a fire, for example. You see the fire in the distance, but you don't know how far away it is. However, to the left of the fire is a fast food restaurant that you know is exactly 1 mile away. Sine, Cosine, Tangent Real World Applications. How to use Sine, Cosine, Tangent Applications. The Sine, Cosine and Tangent functions are often applied to real world scenarios.