a) Ta có: \(a\perp MN,b\perp MN\Rightarrow a//b\)
b) Ta có: \(\widehat{P_1}=\widehat{P_3}=55^0\)(đối đỉnh)
Ta có: \(a//b\Rightarrow\widehat{P_3}=\widehat{Q_5}=55^0\)(đồng vị)
Ta có: \(a//b\Rightarrow\widehat{P_3}+\widehat{Q_4}=180^0\)(trong cùng phía)
\(\Rightarrow\widehat{Q_4}=180^0-55^0=125^0\)
Ta có: \(a//b\Rightarrow\widehat{Q_4}=\widehat{P_2}=125^0\)(so le trong)