Question

Answer 1

a: a//b

DE\(\perp\)a

Do đó: DE\(\perp\)b

b: a//b

=>\(\widehat{B_1}=\widehat{A_1}\)(hai góc đồng vị)

mà \(\widehat{B_1}=120^0\)

nên \(\widehat{A_1}=120^0\)

\(\widehat{A_1}+\widehat{A_2}=180^0\)(hai góc kề bù)

=>\(\widehat{A_2}+120^0=180^0\)

=>\(\widehat{A_2}=60^0\)