In $riangle mathrm{ABC}, angle mathrm{BAC}=90^{circ}$ and $mathrm{AB}=frac{1}{2} mathrm{BC}$. Then the measure of $angle A C B$ is :

If AB = x; BC = 2x unitsIf AB = x; BC = 2x units

$herefore mathrm{AC}=sqrt{4 x^{2}-x^{2}}=sqrt{3} x$

$herefore sin A C B=frac{A B}{B C}=frac{1}{2}=sin 30^{circ}$

$herefore angle A C B=30^{circ}$