**Civil engineers use trigonometry to determine lengths that are not able to be measured to determine angles and to calculate torque.** Trigonometry is a vital part of the planning process of civil engineering, as it aids the engineers in creating structures with exact precision.

Trigonometry is a branch within the larger field of mathematics that studies the relationships of measurements within triangles. All triangles have certain fixed relationships. For instance, one example is that the three angles of a triangle always add up to 180 degrees, no matter what the triangle looks like or how big it is. Trigonometry can be dated back to as early as the third century B.C., where astronomers used triangle properties to determine rough distances and positions of stars and planets. Today, trigonometry has a large variety of applications, one of which is civil engineering.

Before construction of buildings and structures ever begins, there is a long planning and modeling process that engineers must go through. Blueprints are created that give construction workers exact guidelines of how to build the structures. The engineers who design and create these blueprints use trigonometry to determine measurements and angles that would take too long to measure by hand. By finding relationships between triangles in the structure's design, trigonometry speeds up the entire engineering process by using known values to determine unknown variables.