Ta có: \(\widehat{O_1}+\widehat{yOz}=\widehat{xOy}\) (2 góc kề nhau)
hay \(\widehat{O_1}+90^o=120^o\)
=> \(\widehat{O_1}=120^o-90^o=30^o\)
Lại có: \(\widehat{O_3}+\widehat{xOt}=\widehat{xOy}\) (2 góc kề nhau)
hay \(\widehat{O_3}+90^o=120^o\)
\(\Rightarrow\widehat{O_3}=120^o-90^o=30^o\)
Có: \(\widehat{O_1}+\widehat{O_2}+\widehat{O_3}=\widehat{xOy}\) (các góc kề nhau)
hay \(30^o+\widehat{O_2}+30^o=120^o\)
\(\Rightarrow\widehat{O_2}=120^o-30^o-30^o=60^o\)
hay \(\widehat{tOz}=60^o\)
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