Question

Answer 1

a: góc B=góc C=(180-120)/2=30 độ

b: góc B=góc C=(180-30)/2=75 độ

Answer 2

Xét `ΔABC` cân tại `A` có :

\(\widehat{A}+\widehat{B}+\widehat{C}=180^0\)

Mà : \(\widehat{A}=120^0\)

\(\widehat{B}=\widehat{C}\)

`=>` \(\widehat{B}=\widehat{C}=\dfrac{180^0-\widehat{A}}{2}=\dfrac{180^0-120^0}{2}=60^0\)

`=>` \(\widehat{B}=\widehat{C}=\dfrac{60}{2}=30^0\)

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Xét `ΔABC` cân tại `A` có :

\(\widehat{A}+\widehat{B}+\widehat{C}=180^0\)

Mà : \(\widehat{A}=30^0\)

`=>`\(\widehat{B}=\widehat{C}=\dfrac{180^0-\widehat{A}}{2}=\dfrac{180^0-30^0}{2}=150^0\)

`=>` \(\widehat{B}=\widehat{C}=\dfrac{150}{2}=75^0\)