The word trigonometry originates from the Greek for triangle and measure. Hence, it deals with the measurements of triangles such as its sides and angles. The most important trigonometric functions are sinecosine and tangent. Consider the following right-angled triangle.

triangle

Sine, cosine and tangent are defined as follows:

Sine

Sine (sin) of equation (alpha is the angle between the hypotenuse and adjacent) is defined by the ratio of the opposite to the hypotenuse.

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Cosine

Cosine (cos) of equation is defined by the ratio of the adjacent to the hypotenuse.

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Tangent

Tangent (tan) of equation is defined by the ratio of the opposite to the adjacent or by the ratio of sine to cosine.

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