This document provides instructions on how to use trigonometry to find an unknown side of a right-angled triangle given one known side and the angle opposite the unknown side. It gives an example of using tangent to find the height of a triangle when the base is 75m and the angle is 30 degrees, obtaining a height of 43.5m. It then instructs the reader to use the same method to find the unknown side of their own right-angled triangle.