Answer: sqrt(3)
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Work Shown:
The tangent ratio involves the opposite over adjacent.
tan(angle) = opposite/adjacent
tan(A) = BC/AC
tan(A) = sqrt(75)/5
tan(A) = ( 5*sqrt(3) )/5 .... see the section below
tan(A) = sqrt(3)
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sqrt(75) = sqrt(25*3)
sqrt(75) = sqrt(25)*sqrt(3)
sqrt(75) = 5*sqrt(3)