TRIGONOMETRIC RATIOS
Introduction:
The word ‘ trigonometry’ is derived from the Greek roots .. ‘tri’ means ‘three’ ; ‘gonia’ means ‘an angle’ ; and metron’ means ‘ meaning ‘ measure’. Thus ‘trigonometry’ means three angle measure. It is analytical study of a three angled geometric figure -- namely the triangle.
Hipparchus ( 140BC ) , a Greek mathematician established the relationships between the sides and angles of a triangle. Greek trigonomentry was further developed by Hindu Mathematicians. They replaced the chords used by the Greeks by half chords of circles with given radii i.e ., the equivalent of our sine functions. The earliest such tables are in siddantas ( systems of Astronomy) of the 4th and 5th centuries A.D. Like numbers, modern trigonometry migreted from the Hindus to Europe via Arabs.
The study of trigometry is of great importance in several fields - for example : in Surverying, Astronomy, Navigation and Engineering. In recent times, trigonometry is widely applied in many branches of Science and Engineering such as Seismology, design of electrical circuits, estimating the heights of tides in ocean etc.