SSC Mathematics Note 9th Chapter Trigonometric Ratio. In our day to day life we make use of triangles, and in particular, right-angled triangles. Many different examples of our surroundings can be drawn where right triangles can be imagined to be formed. In ancient times, with the help of geometry men learned the technique of determining the width of a river by standing on its bank. Without climbing the tree they knew how to measure the height of the tree accurately by comparing its shadow with that of a stick. In all the situations given above, the distances or heights can be found by using some mathematical technique which come under a special branch of mathematics called Trigonometry.

## SSC Mathematics Note 9th Chapter Trigonometric Ratio

The word ‘Trigonometry’ is derived from the Greek words ‘tri’ (means three), ‘gon’ (means edge) and `metron’ (means measure). In fact, trigonometry is the study of the relationship between the sides and angles of a triangle. There is evidence of using the Trigonometry in Egyptian and Babylonian civilization. It is believed that the Egyptians made its extensive use in land survey and engineering works. Early astrologer used it to determine the distances from the Earth to the farthest planets and stars. At present trigonometry is in use in all branches of mathematics. There are wide usages of trigonometry for the solution of triangle related problems and in navigation etc. Nowadays trigonometry is in wide use in Astronomy and Calculus.

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