$\sqrt{{{2}^{2}}-1}=OB=\sqrt{3}$  $BC=\sqrt{{{2}^{2}}+1}=\sqrt{5}$  $AB=\sqrt{{{2}^{2}}+{{(\sqrt{5})}^{2}}}=\sqrt{4+5}=\sqrt{9}=3$  $OA=OB=AB=\sqrt{3}+3=3+\sqrt{3}$