Question

Answer 1

a: Ta có: Ax//By

=>\(\widehat{xAD}=\widehat{CDB}\)(hai góc so le trong)

=>\(\widehat{CDB}=50^0\)

b: Xét ΔCDB có \(\widehat{CDB}+\widehat{CBD}+\widehat{DCB}=180^0\)

=>\(\widehat{DCB}=180^0-50^0-40^0=90^0\)

Ta có: \(\widehat{ACB}+\widehat{DCB}=180^0\)(hai góc kề bù)

=>\(\widehat{ACB}=180^0-90^0=90^0\)