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Secant is the reciprocal of the cosine function which is adjacent side divided by the hypotenuse. Thus secant is the hypotenuse divided by the adjacent side. The opposite side is the one that theta faces (in this case the side with length 3). The adjacent side is length 4 and the hypotenuse is length 5. Secant is hypotenuse divided by adjacent so it is 5/4. The answer is A.
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