ETYM Greek trigonon a triangle + -metry: cf. French trigonométrie. Related to Trigon.
The mathematics of triangles and trigonometric functions; SYN. trig.
Mathematical study of triangles and measurement by deducing unknown from known sides and angles.
Branch of mathematics that solves problems relating to plane and spherical triangles. Its principles are based on the fixed proportions of sides for a particular angle in a right-angled triangle, the simplest of which are known as the sine, cosine, and tangent (so-called trigonometrical ratios). It is of practical importance in navigation, surveying, and simple harmonic motion in physics.
Invented by Hipparchus, trigonometry was developed by Ptolemy of Alexandria and was known to early Hindu and Arab mathematicians.
The branch of mathematics dealing with arcs and angles, expressed in functions (for example, sine and cosine) that show relationships—for example, between two sides of a right triangle or between two complementary angles.