Bài 1:
\(\hat{C}_1=360\text{˚}-110\text{˚}-60\text{˚}-75\text{˚}=115\text{˚}\)
\(\hat{C}_2=180\text{˚}-115\text{˚}=65\text{˚}\)
==========
Bài 2: Do AB // CD nên:
a/ \(x=180\text{˚}-75\text{˚}=105\text{˚}\)
\(y=180\text{˚}-40\text{˚}=140\text{˚}\)
------------
b/ \(x=80\text{˚}\left(đv\right)\)
\(y=40\text{˚}\left(slt\right)\)
----------
c/ \(x=180\text{˚}-90\text{˚}=90\text{˚}\)
\(y=180\text{˚}-45\text{˚}=135\text{˚}\)
==========
Bài 3: (đề sai, AB // CD hợp lí hơn)
Ta có: \(\left\{{}\begin{matrix}\hat{A}-\hat{D}=30\text{˚}\\\hat{A}+\hat{D}=180\text{˚}\end{matrix}\right.\)
\(\left\{{}\begin{matrix}\hat{B}=2\hat{C}\\\hat{B}+\hat{C}=180\text{˚}\end{matrix}\right.\)
Vậy: \(\left\{{}\begin{matrix}\hat{A}=115\text{˚}\\\hat{B}=120\text{˚}\\\hat{C}=60\text{˚}\\\hat{D}=75\text{˚}\end{matrix}\right.\)
