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For an acute angle θ of a right triangle, the cosine of θ is the ratio between the lengths of the adjacent side and the hypotenuse.
The cosine of θ is written as cos θ.
cos θ=Adjacent/Hypotenuse
While this trigonometric ratio expresses the ratio of the adjacent side to the hypotenuse, it does not state the actual measurements of their lengths.
It should be noted that for a given angle, when the adjacent side and hypotenuse lengths change, if their ratio stays the same, then the cosine, too, would stay the same.