a: \(\widehat{yOz}=100^0-30^0=70^0\)
b: \(\widehat{zOm}=\dfrac{\widehat{xOz}}{2}\)
\(\widehat{zOn}=\dfrac{\widehat{yOz}}{2}\)
Do đó: \(\widehat{zOm}+\widehat{zOn}=\dfrac{1}{2}\left(\widehat{xOz}+\widehat{yOz}\right)\)
hay \(\widehat{mOn}=\dfrac{1}{2}\cdot\widehat{xOy}\)