\(A+C=;B+C\)
KL: \(A=B\)
CM:\(A+C=B+C\)
\(A+C-C=B+C-C\)
\(\Leftrightarrow A=B\)
\(\LeftrightarrowĐPCM\)
Ta có:
\(\widehat{xOy} + \widehat{yOx'} = 180^O\)(kề bù)
\(\widehat{xOy} + \widehat{xOy'} =180^O\)(kề bù)
\(\Rightarrow\)\(\widehat{yOx'} = \widehat{xOy'}\)