**Trigonometry is used in many fields of applied and practical sciences, such as astronomy, geography, physics and engineering.** Trigonometry is used in astronomy to determine the distance from Earth to various nearby stars by observing the parallax shift with Earth's orbit around the Sun as a baseline.

Trigonometry is useful in geography for surveying prominent landforms and projecting physical features onto maps and globes. In physics, trigonometry is one of the most heavily used mathematical disciplines. It is used to calculate the refractive index of glass, which permits the manufacture of telescopes, microscopes and fiber optic cables, and to better understand physical spaces. Engineers make practical use of trigonometry when determining the angles and design of support structures. A grasp of trigonometry gives engineers a theoretical understanding of distances, load capacities and lines of force. Chemical engineers routinely use trigonometry to predict the natural structure and consequent behavior of the molecules they work with. Beyond these specific applications, trigonometry has a use for nearly any theoretical or practical application that entails the use of space, volume or distance. It also has implications within theoretical mathematics because the way a hypothetical curve arcs through n-space can be described with almost the same equation as the arc of a coastline on a map.