Câu hỏi 9.11
92
Cho \(\triangle \mathrm{ABC} \sim \triangle \mathrm{DEF}\). Biết \(\widehat{A}=60^{\circ}, \widehat{E}=80^{\circ}\), hãy tính số đo các góc \(\widehat{B}, \widehat{C}, \widehat{D}, \widehat{F}\).
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Vì \(\triangle \mathrm{ABC} \sim \triangle \mathrm{DEF}\). Suy ra \(\widehat{A}=\widehat{D} ; \widehat{B}=\widehat{E} ; \widehat{C}=\widehat{F}\).
Mà \(\widehat{A}=60^{\circ} \Rightarrow \widehat{D}=60^{\circ} ; \widehat{E}=80^{\circ}\) nên \(\widehat{B}=80^{\circ}\).
Có \(\widehat{A}+\widehat{B}+\widehat{C}=180^{\circ}\), suy ra \(\widehat{C}=\widehat{F}=180^{\circ}-60^{\circ}-80^{\circ}=40^{\circ}\).