Ta có: Ox//HK suy ra $\widehat{KOx}=\widehat{OKH} $ (hai góc so le trong); $\widehat{xOy}=\widehat{OHK}$(hai góc đồng vị)
=> $\widehat{OHK}=\widehat{OKH}$
Ta có: Ox//HK suy ra $\widehat{KOx}=\widehat{OKH} $ (hai góc so le trong); $\widehat{xOy}=\widehat{OHK}$(hai góc đồng vị)
=> $\widehat{OHK}=\widehat{OKH}$