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# What is Trigonometry? Find out what the branch of math known as trigonometry is all about.

By
Jason Marshall, PhD As you might be able to guess from the first part of the word, the branch of mathematics known as trigonometry is all about triangles. In particular, it’s about how the three sides and three angles of a triangle are related. The word trigonometry comes from the Greek words trigon meaning—no big surprise here—triangle, and metron meaning something like “measure.” Which makes a lot of sense since trigonometry is all about figuring out clever ways to measure and calculate the properties of the components of triangles. As such, it’s also really just a specialized branch of geometry…which is the part of math that looks at points, lines, planes, and shapes.

Chief among the useful methods and tools for dealing with triangles in trigonometry are the trigonometric functions—sine, cosine, and tangent. These three functions can be combined together in an amazing number of ways to calculate unknown properties of a given triangle (the length of one of its legs or the value of one of its angles) given some combination of its known properties. Among its many frequently demonstrated practical applications, trigonometry can be used to figure out how tall a building is just by knowing how far you are from the building and what angle the top of the building makes with the ground…very cool stuff! 