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# Trigonometry

Trigonometry is a branch of geometry used in diverse fields like navigation, surveying, engineering, astronomy, architecture, etc. It involves the study of triangles and its measurements.

The word trigonometry is derived from Greek works ‘trigon’ meaning a triangle, and ‘metron’ meaning measurement.

There are three main trigonometric ratios – sine, cosine and tangent. We will study the path of sine, cosine and tangent trigonometric functions and their properties. We will sketch the graph of these functions and their inverses, and look at the relationship between the trigonometric ratios and functions.

We will also use these ratios in conjunction with known dimensions of the sides of a triangle to find the other unknown sides of the triangle. For example, if we have a right-angled triangle, we can get the third side applying the Pythagoras rule. But if we are only given an angle and a side, we can use the trigonometric ratios to find the unknown side.

Sometimes the figure under consideration may not be a right-angled triangle. In that case, we use the sine or cosine rule to find the unknown sides and angles.

One of the applications of trigonometry is in orienteering to find the distance and direction with compass bearings.

We use an instrument called ‘clinometry’ to find the angle between the horizontal surface and the object under consideration (line of sight) from your eye.

Here are some more topics in trigonometry:

Trigonometric ratios

Angle measurement

Calculating angle sizes, and so on..