Answer: 19.1
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Work Shown:
tan(angle) = opposite/adjacent
tan(C) = AB/BC
tan(theta) = x/BC
tan(23) = (8.1)/BC
BC*tan(23) = 8.1
BC = (8.1)/tan(23)
BC = 19.0824041631723
BC = 19.1
In this case, rounding to 3 sig figs means we round to the nearest tenth.
Make sure your calculator is in degree mode.