CÓ +)$d'//d''\Rightarrow \widehat{E_{1}}=\widehat{C}=60^o$(2 góc so le trong)+)$d'//d''\Rightarrow \widehat{G_{2}}=\widehat{D}=110^o$(2 góc đồng vị)+)$\widehat{G_{3}}+\widehat{G_{2}}=180^o$(2 góc kề nhau)$\Leftrightarrow \widehat{G_{3}}=180^o-\widehat{G_{2}}=180^o-110^o=50^o$+)$\widehat{D_{4}}=110^o$(2 góc đối đỉnh)+)$\widehat{ACD}=\widehat{C}=60^o$(2 góc đối đỉnh)$d//d'\Rightarrow \widehat{A_{5}}=\widehat{ACD}=60^o$(2 góc so le trong)+)$d//d''\Rightarrow \widehat{B_{6}}=\widehat{G_{3}}=50^o$

CÓ +)$d'//d''\Rightarrow \widehat{E_{1}}=\widehat{C}=60^o$(2 góc so le trong)+)$d'//d''\Rightarrow \widehat{G_{2}}=\widehat{D}=110^o$(2 góc đồng vị)+)$\widehat{G_{3}}+\widehat{G_{2}}=180^o$(2 góc kề nhau)$\Leftrightarrow \widehat{G_{3}}=180^o-\widehat{G_{2}}=180^o-110^o=70^o$+)$\widehat{D_{4}}=110^o$(2 góc đối đỉnh)+)$\widehat{ACD}=\widehat{C}=60^o$(2 góc đối đỉnh)$d//d'\Rightarrow \widehat{A_{5}}=\widehat{ACD}=60^o$(2 góc so le trong)+)$d//d''\Rightarrow \widehat{B_{6}}=\widehat{G_{3}}=70^o$