x=70+45=115 độ
y=180-80-75=100-75=25 độ
Xét tam giác ABD ta có:
\(\widehat{BAD}+\widehat{B}+\widehat{BDA}=180^o\)
\(\Rightarrow\widehat{BDA}=180^o-\widehat{BAD}-\widehat{B}=180^o-75^o-40^o=65^o\)
Mà: \(\widehat{BDA}+\widehat{ADC}=180^o\) (hai góc kề bù)
\(\Rightarrow\widehat{ADC}=x=180^o-\widehat{BDA}=180^o-65^o=115^o\)
Xét tam giác ABC ta có:
\(\widehat{A}+\widehat{B}+\widehat{C}=180^o\)
\(\Rightarrow\left(\widehat{BAD}+\widehat{DAC}\right)+\widehat{B}+\widehat{C}=180^o\)
\(\Rightarrow\widehat{C}=y=180^o-\left(40^o+40^o\right)-75^o=25^o\)
\(\widehat{D}=180-\widehat{A1}-\widehat{B}=65^o\)
mà \(\widehat{x}\) kề bù \(\widehat{D}\) =>góc x=180-góc D=115độ
góc y = 180 - góc A2 - góc x = 25 độ
