`hatM_1 - hatN_1 = 50^@ `

`-> hatM_1 = 50^@ + hatN_1`

`a////b`

`-> hatM_1 + hatN_1 = 180^@` ( trong cùng phía )

`=> 50 + hatN_1 + hatN_1 =180^@`

`=> 2hatN_1 = 130^@`

`=> hatN_1 = 65^@`

`=> hatM_1 = 65^@ + 50^@ = 115^@`

`=> hatM_2 = hatN_1 = 65^@`

`=> hatN_2 = hatM_1 = 115^@`

Vì `a //// b` (gt)

`=> \hat(M_1)+\hat(N_1)=180^0` (trong cùng phía)

Mà `\hat(M_1)-\hat(N_1)=50^0`

`=> \hat(M_1)=(180^0 +50^0)/2=115^0`

`->\hat(N_1)=180^0 -\hat(M_1)=180^0 -115^0=65^0`

Vì `a //// b` (gt)

`=> \hat(M_1)=\hat(N_2)  (=115^0)` (so le trong)

`-> \hat(N_2)=115^0`
Và: `\hat(N_1)=\hat(M_2) (=65^0)` (so le trong)

`-> \hat(M_2)=65^0`