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2/$AB//CD$ $\Rightarrow\widehat{ABC}+\widehat{ACB}=180^0$$\Rightarrow\widehat{ABC}=180^0-\widehat{ACB}=180^0-30^0=150^0$$\widehat{xBC}=\widehat{BCD}=30^0$

2/$AB//CD\Rightarrow \widehat{ABC}+\widehat{ACB}=180^0$$\Rightarrow\widehat{ABC}=180^0-\widehat{ACB}=180^0-30^0=150^0$$\widehat{xBC}=\widehat{BCD}=30^0$

AB//CD" role="presentation" style="font-size: 13.696px; display: inline; word-spacing: 0px; position: relative; background-color: rgb(255, 255, 255);">AB//CDAB//CD ⇒C^+ABC^=1800⇒ABC^=1800−300=1500" role="presentation" style="font-size: 13.696px; display: inline; word-spacing: 0px; position: relative; background-color: rgb(255, 255, 255);">⇒Cˆ+ABCˆ=1800⇒ABCˆ=1800−300=1500⇒C^+ABC^=1800⇒ABC^=1800−300=1500 xBC^=DBC^=300" role="presentation" style="font-size: 13.696px; display: inline; position: relative;">xBCˆ=DCBˆ=300xBC^=DBC^=300 (2 góc ở vị trí so le trong)

2/$AB//CD$ $\Rightarrow\widehat{ABC}+\widehat{ACB}=180^0$$\Rightarrow\widehat{ABC}=180^0-\widehat{ACB}=180^0-30^0=150^0$$\widehat{xBC}=\widehat{BCD}=30^0$

AB//CD" role="presentation" style="font-size: 13.696px; display: inline; word-spacing: 0px; position: relative; background-color: rgb(255, 255, 255);">B//CDAB//CD ⇒C^+ABC^=1800⇒ABC^=1800−300=1500" role="presentation" style="font-size: 13.696px; display: inline; word-spacing: 0px; position: relative; background-color: rgb(255, 255, 255);">⇒Cˆ+ABCˆ=1800⇒ABCˆ=1800−300=1500⇒C^+ABC^=1800⇒ABC^=1800−300=1500 xBC^=DBC^=300" role="presentation" style="font-size: 13.696px; display: inline; position: relative;">xBCˆ=DCBˆ=300xBC^=DBC^=300 (2 góc ở vị trí so le trong)

AB//CD" role="presentation" style="font-size: 13.696px; display: inline; word-spacing: 0px; position: relative; background-color: rgb(255, 255, 255);">AB//CDAB//CD ⇒C^+ABC^=1800⇒ABC^=1800−300=1500" role="presentation" style="font-size: 13.696px; display: inline; word-spacing: 0px; position: relative; background-color: rgb(255, 255, 255);">⇒Cˆ+ABCˆ=1800⇒ABCˆ=1800−300=1500⇒C^+ABC^=1800⇒ABC^=1800−300=1500 xBC^=DBC^=300" role="presentation" style="font-size: 13.696px; display: inline; position: relative;">xBCˆ=DCBˆ=300xBC^=DBC^=300 (2 góc ở vị trí so le trong)