TA CÓ: OI LÀ TIA NẰM GIỮA OA; OB
\(\Rightarrow\widehat{AOI}+\widehat{IOB}=\widehat{AOB}\)
MÀ: \(\widehat{AOI}=\frac{1}{4}\widehat{IOB}\)
THAY SỐ: \(\frac{1}{4}\widehat{IOB}+\widehat{IOB}=70^0\)
\(\Rightarrow\left(\frac{1}{4}+1\right)\widehat{IOB}=70^0\)
\(\frac{5}{4}\widehat{IOB}=70^0\)
\(\widehat{IOB}=70^0:\frac{5}{4}\)
\(\Rightarrow\widehat{IOB}=56^0\)
MÀ \(\widehat{AOI}=\frac{1}{4}\widehat{IOB}\)
THAY SỐ: \(\widehat{AOI}=\frac{1}{4}.56^0=14^0\)
\(\Rightarrow\widehat{AOI}=14^0\)
CHÚC BN HỌC TỐT!!!!!