a: Ta có: \(\hat{A_1}=\hat{A_3}\) (hai góc đối đỉnh)
mà \(\hat{A_1}+\hat{A_3}=100^0\)
nên \(\hat{A_1}=\hat{A_3}=\frac{100^0}{2}=50^0\)
Ta có: \(\hat{A_3}+\hat{A_4}=180^0\) (hai góc kề bù)
=>\(\hat{A_4}=180^0-50^0=130^0\)
b: Ta có: \(\hat{A_1}+\hat{A_2}=180^0\)
mà \(\hat{A_1}-\hat{A_2}=100^0\)
nên \(\hat{A_1}=\frac{180^0+100^0}{2}=140^0\)
=>\(\hat{A_2}=140^0-100^0=40^0\)
Ta có: \(\hat{A_3}=\hat{A_1}\) (hai góc đối đỉnh)
mà \(\hat{A_1}=140^0\)
nên \(\hat{A_3}=140^0\)
Ta có: \(\hat{A_2}=\hat{A_4}\) (hai góc đối đỉnh)
mà \(\hat{A_2}=40^0\)
nên \(\hat{A_4}=40^0\)
c: Ta có: \(\hat{A_4}+\hat{A_1}=180^0\) (hai góc kề bù)
=>\(2\cdot\hat{A_1}+\hat{A_1}=180^0\)
=>\(3\cdot\hat{A_1}=180^0\)
=>\(\hat{A_1}=\frac{180^0}{3}=60^0\)
\(\hat{A_4}=2\cdot\hat{A_1}=120^0\)
Ta có: \(\hat{A_3}=\hat{A_1}\) (hai góc đối đỉnh)
mà \(\hat{A_1}=60^0\)
nên \(\hat{A_3}=60^0\)