The cosine function is one of the three primary trigonometric functions. In a right triangle, the cosine is the ratio between the length of the side adjacent to the angle and the length of the hypotenuse.
cosθ = AdjacentHypotenuse
Special values of cosine
Notice the pattern
Explore by rotating the hypotenuse about the circle's center. By calculating the ratio adjacent/hypotenuse for different values of θ, we can construct the graph of cosθ. Change the value of r with the slider and notice that this ratio is not affected.
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