9514 1404 393
Answer:
15/17
Explanation:
cos(arctan(8/15)) = 15/17
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You could assume the ratio values 8 and 15 represent the opposite and adjacent sides of a right triangle. Then the hypotenuse is ...
h = √(8² +15²) = √289 = 17
The cosine is the ratio of the adjacent side to the hypotenuse, so is ...
cos(x) = 15/17