Ta có:
`hat{I_{4}} = hat{I_{2}} = 54^o` (đối đỉnh)
`hat{I_{4}} + hat{I_{1}} = 180^o` (kề bù)
`⇒ hat{I_{1}} = 180^o - 54^o = 126^o`
`hat{I_{1}} = hat{I_{3}} = 126^o` (đối đỉnh)
Vì: `m //// n` nên:
`hat{I_{4}} = hat{K_{2}} = 54^o` (so le trong)
`hat{I_{4}} = hat{K_{4}} = 54^o` (đồng vị)
`hat{I_{3}} = hat{K_{1}} = 126^o` (so le trong)
`hat{I_{3}} = hat{K_{3}} = 126^o` (đồng vị)
Vậy: `hat{I_{4}} = hat{K_{4}} = hat{K_{2}} = hat{I_{2}} = 54^o`
`hat{I_{1}} = hat{I_{3}} = hat{K_{3}} = hat{K_{1}} = 126^o`
