Question

Answer 1

a: 

GT	\(a\cap c=\left\{A\right\}\) \(b\cap c=\left\{B\right\}\) \(\widehat{A_1}+\widehat{B_1}=180^0;\widehat{A_1}=2\cdot\widehat{B_1}\)
KL	\(\widehat{A_1}=?;\widehat{B_1}=?\) a//b

b: \(\widehat{A_1}+\widehat{B_1}=180^0\)(hai góc bù nhau)

mà \(\widehat{A_1}=2\cdot\widehat{B_1}\)

nên \(2\cdot\widehat{B_1}+\widehat{B_1}=180^0\)

=>\(\widehat{B_1}=\dfrac{180^0}{2+1}=60^0\)

=>\(\widehat{A_1}=2\cdot\widehat{B_1}=120^0\)

\(\widehat{A_1}+\widehat{B_1}=180^0\)

mà hai góc này là hai góc ở vị trong cùng phía

nên a//b