### Trigonometric Functions

Trigonometry is a field of mathematics, whose term is derived from geek: *trigon*
(triangle) and *metron* (measure) that is the triangle measures. The triangle has three sides and three angles.
The longest side of a right triangle is called hypotenuse. If the measures of two sides are known, we use the
Pythagorean Theorem to calculate the length of the hypotenuse.

The formula of the Pythagorean Theorem is c^{2} = a^{2} + b^{2}, where:

hypotenuse = c = √ a^{2}+b^{2}) .

The measures of angles can be expressed in radians or degrees. To convert the radians to degrees (or vice versa) are
used the formulas below:

a) degrees to radians : multiply the number of degree by Π / 180;

b) radians to degrees : multiply the number of radian by 180 / Π

From the triangles inscribed in quadrants of a circle and its Cartesians measures, we can calculate the sine, cosine,
tangent, cotangent, secant and cosecant for each quadrant.

We list below the main trigonometric identities:

sine (x) = opposite side / hypotenuse;

cosine (x) = adjacent side / hypotenuse;

tangent (x) = sin (x) / cosine (x);

cotangent (x) = 1 / tangent (x) ;

secant (x) = 1 / cosine (x) ;

cosecant (x) = 1 / sine (x) ;

sine^{2}a + cosine^{2}b = 1.

Finally we reported that trigonometry has many uses in diverse fields such as engineering, medicine, astronomy, acoustics, geography, astronomy etc.

It is also widely used in theodolites and indirect measurements of inaccessible locations.

How to calculate the **Trigonometric Functions.**

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