Sine , Cosine and Tangent (often shortened to sin , cos and tan ) are each a ratio of sides of a right angled triangle:

Have a try! Move the mouse around to see how different angles (in radians or degrees ) affect sine, cosine and tangent.

Notice that the adjacent side and opposite side can be positive or negative, which makes the sine, cosine and tangent change between positive and negative values also.

The classic 30° triangle has a hypotenuse of length 2, an opposite side of length 1 and an adjacent side of
√ 3 :

Try this paper-based exercise where you can calculate the sine function for all angles from 0° to 360°, and then graph the result. It will help you to understand these relatively simple functions.

To complete the picture, there are 3 other functions where we divide one side by another, but they are not so commonly used.

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