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From where do we get the name of trigonometric ratios |
| Answer» It\'s easiest to think of the trig functions on a circle- this is how they were constructed before calculators.\tSine is from the Latin for bay and/or the Arabic for bowstring. Picture the chord (segment from A-B) and the circle A-D-B as a bow. If you measure the length of A-C and divide by the radius of the circle (O-A) you get the sine of the angle theta\tCosine is from "complement sin". It\'s the complement to the angle, so if you measure the distance from the centre to the chord (O-C) and divide by the radius you get the cos of the angle.\tTangent is from the Latin for touch. A tangent is a line that touches the circle once. By definition this meets a line to the centre at right angle, so you always have a right angle triangle and so an easy definition of the tan of the angle.\tSecant is from cut (Latin again). It cuts the tangent from O-E cosecant,\tCotangent etc are like cosine, the complements to their respective functions, but unless you do a lot of maths you probably won\'t meet them | |