a, Kẻ Oz//Ax//By
Ta có \(\widehat{zOA}=\widehat{xAO}=35^0\left(so.le.trong\right);\widehat{zOC}=180^0-\widehat{OCy}=20^0\left(trong.cùng.phía\right)\)
\(\Rightarrow\widehat{AOC}=\widehat{zOA}+\widehat{zOC}=35^0+20^0=55^0\)
b, OA ko vuông góc OC vì \(\widehat{AOC}=55^0\ne90^0\)