Do AD//BE \(\Rightarrow\widehat{EAD}=180^o-\widehat{AEB}=180^o-50^o=130^o\)
Có: \(\widehat{FAD}=180^o-\widehat{AFC}=180^o-40^o=140^o\)
\(\Rightarrow\widehat{EAF}=360^o-\widehat{EAD}-\widehat{FAD}=360^o-140^o-130^o=90^o\)
có : EB//DA
`=> góc BEA + góc DAF = 180^0`( trong cùng phía bù nhau)
`=> 50^0 + DAF = 180^0`
`=> góc DAF = 130^0`
có : AD//CF
`=> DAF + CFA = 180^0`( TCP bù nhau)
`=> DAF + 40^0 = 180^0`
`=> DAF = 140^0`
Lại có :
`EAD + DAF + EAF + 360^0`
`=> 130^0 + 140^0 + EAF = 360^0`
`=> 270^0 + EAF = 360^0`
`=> EAF = 90^0`
