Chỉ mik bài này vs ạ

Ta có: `a////b` `(`gt`)`

`=>` `\hat(A_1) + \hat(B_2) = 180^@` `(2` góc trong cùng phía`)`

`=>` `\hat(B_2) = 180^@ - \hat(A_1) = 180^@ - 140^@ = 40^@`

`=>` `\hat(ABC) = \hat(B_1) + \hat(B_2) = 60^@ + 40^@ = 100^@`

Ta có: `b////c` `(`gt`)`

`=>` `\hat(B_1)=\hat(C_1)` `(2` góc so le trong`)`

`=>` `\hat(C_1) = 60^@`

mà `\hat(C_1) + \hat(C_2) = 180^@` `(2` góc kề bù`)`

`=>` `\hat(C_2) = 180^@ - \hat(C_1) = 180^@ - 60^@ = 120^@`

`#vu0000`