a) Ta có: \(\widehat{C_1}-\widehat{C_2}=40^0\left(gt\right),\widehat{C_1}+\widehat{C_2}=180^0\)(2 góc kề bù)
\(\Rightarrow\left\{{}\begin{matrix}\widehat{C_1}=\left(180^0+40^0\right):2=110^0\\\widehat{C_2}=\left(180^0-40^0\right):2=70^0\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}\widehat{D_1}=\widehat{C_2}=110^0\\\widehat{D_2}=\widehat{C_1}=70^0\end{matrix}\right.\)(2 cặp góc so le trong)
b) Ta có: \(\widehat{C_1}+\widehat{CDb}=180^0\)(2 góc trong cùng phía)
Mà \(\widehat{CDb}=\widehat{D_2}\)(2 góc đối đỉnh)
\(\Rightarrow\widehat{C_1}+\widehat{D_2}=180^0\)
Mà \(\widehat{C_1}-\widehat{D_2}=30^0\)
\(\Rightarrow\left\{{}\begin{matrix}\widehat{C_1}=\left(180^0+30^0\right):2=105^0\\\widehat{D_2}=\left(180^0-30^0\right):2=75^0\end{matrix}\right.\)
\(\Rightarrow\widehat{C_2}=\widehat{D_2}=75^0\)(2 góc đồng vị)
a,C1+C2=180 và C1-C2=40 nên C1=110,C2=70
suy ra D1=C2=80(so le trong)
D2=C1=110(so le trong)
b,D2=C2(đồng vị)
nên C1-D2=C1-C2=30 mà C1+C2=180
nên C1=105,C2=75
suy ra D1=C1=105(dồng vị)
D2=C2=75(đồng vị)
tick mik nha
