Question

Answer 1

\(a,\left\{{}\begin{matrix}IB=IA\\IA=IC\end{matrix}\right.\Rightarrow IB=IA=IC=\dfrac{1}{2}BC\\ \Rightarrow\Delta ABC\text{ vuông tại }A\\ \Rightarrow\widehat{BAC}=90^0\\ b,\left\{{}\begin{matrix}IO\text{ là p/g }\widehat{AIB}\\IO'\text{ là p/g }\widehat{AIC}\end{matrix}\right.\\ \text{Mà }\widehat{AIB}+\widehat{AIC}=180^0\\ \Rightarrow IO\bot IO'\Rightarrow\widehat{OIO'}=90^0\\ c,\text{Áp dụng HTL: }IA=\sqrt{OA\cdot O'A}=6\left(cm\right)\\ \Rightarrow BC=2IA=12\left(cm\right)\)