`\hat{A}/2=\hat{B}/2`
`⇒\hat{A}=\hat{B}`
a) `\hat{A}+\hat{B}=90^0`
`⇒\hat{A}=\hat{B}=90^0/2=45^0`
b `\hat{A}+\hat{B}=180^0`
`⇒\hat{A}=\hat{B}=180^0/2=90^0`
c) `\hat{B}-\hat{A}=10^0` mà `\hat{A}=\hat{B}`
`⇒` ko tồn tại `\hat{A}, hat{B}`
d) `\hat{A}+3\hat{B}=120^0`
`⇒4\hat{A}=4\hat{B}=120^0`
`⇒\hat{A}=\hat{B}=120^0/4=30^0`
