Xét \(\Delta DEF\) có:
\(\widehat{D}+\widehat{E}+\widehat{F}=180^0\) (định lí tổng 3 góc trong một tam giác).
=> \(60^0+\widehat{E}+\widehat{F}=180^0\)
=> \(\widehat{E}+\widehat{F}=180^0-60^0\)
=> \(\widehat{E}+\widehat{F}=120^0.\)
Mà \(\widehat{E}=2\widehat{F}\left(gt\right)\)
=> \(2\widehat{F}+\widehat{F}=120^0\)
=> \(3\widehat{F}=120^0\)
=> \(\widehat{F}=120^0:3\)
=> \(\widehat{F}=40^0.\)
=> \(\widehat{E}+40^0=120^0\)
=> \(\widehat{E}=120^0-40^0\)
=> \(\widehat{E}=80^0.\)
Vậy \(\widehat{E}=80^0;\widehat{F}=40^0.\)
Chúc bạn học tốt!
