Question

Tam giác ABC có \(\widehat{A}\) = 75^o. Tính \(\widehat{B}\) và \(\widehat{C}\), biết :

a) \(\widehat{B}\) = 2\(\widehat{C}\)

b) \(\widehat{B}\) - \(\widehat{C}\) = 25^o

Các bạn giúp mình với, nhanh nhé, mình đang cần gấp !!!!

Answer 1

Ta có : \(\widehat{B}+\widehat{C}=180^o-\widehat{A}=180^o-75^o=105^o\)

a/ \(\widehat{B}=2\widehat{C}\Rightarrow2\widehat{C}+\widehat{C}=105^o\Rightarrow3\widehat{C}=105^o\Rightarrow\widehat{C}=35^o\Rightarrow\widehat{B}=70^o\)

b/ \(\widehat{B}-\widehat{C}=25^o\Rightarrow\widehat{B}=\widehat{C}+25^o\Rightarrow\widehat{C}+25^o+\widehat{C}=105^o\Rightarrow2\widehat{C}=80^o\Rightarrow\widehat{C}=40^o\Rightarrow\widehat{B}=65^o\)