- Hình 23a: \(\widehat {xOy} = {27^o},\,\,\widehat {yOz} = {63^o},\,\,\widehat {xOz} = {90^o}\)
Suy ra: \(\widehat {xOy} + \widehat {yOz} = {27^o} + {63^o} = {90^o}\)
- Hình 23b:
\(\widehat {xOy} = {30^o},\,\,\widehat {yOz} = {80^o},\)\(\widehat {xOz} = {110^o}\)
Suy ra: \(\widehat {xOy} + \widehat {yOz} = {30^o} + {80^o} \)\(= {110^o} = \widehat {xOz}\)
