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cosine function
The graph of y = cos x
The cosine function, cos α, is the ratio of the side adjacent to the angle α to the hypotenuse in a right-angled triangle. It is a trigonometric function.

If the x-axis is extended, the graph of y = cos x repeats itself every 360, i.e. the period of the cosine function is 360.

See also cosine rule.

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