Cách làm cho bạn:
Ta có: AB = AC nên tam giác ABC cân ở A, Do đó \(\widehat{B}\) = \(\widehat{C}\)
a) \(\widehat{A}\) = 1450
Trong ∆ABC : \(\widehat{A}\) + \(\widehat{B}\) + \(\widehat{C}\) = 1800
mà \(\widehat{B}\) = \(\widehat{C}\)
=> \(\widehat{A}\) + 2\(\widehat{B}\) = 1800
=>2\(\widehat{B}\) = 1800- \(\widehat{A}\) = 1800- 1450
=> \(\widehat{B}\) = 22,50
b) \(\widehat{A}\) = 1000
Tương tự với câu a \(\widehat{A}\) + 2\(\widehat{B}\) = 1800
=>2\(\widehat{B}\) = 1800- \(\widehat{A}\) = 1800- 1000
=> \(\widehat{B}\) = 400
vậy \(\widehat{ABC}\)=400
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