Answer:
61.9°
Explanation:
The mnemonic SOH CAH TOA reminds you that ...
Tan = Opposite/Adjacent
Then in your triangle, you have ..
tan(x°) = 15/8
x° = arctan(15/8) ≈ 61.9°
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"arctan(...)" can be read as "the angle whose tangent is ..." The calculator function that gives this value is often a "2nd" function, overlaid on the key that gives you the tangent. It may be labeled tan⁻¹.