a, cho tam giac ABC va tam giac A\(_1\)B\(_1\)C\(_1\) co AB=A\(_1\)B\(_1\), AC=A\(_1\)C\(_1\) va BC > B\(_1\)C\(_1\). So sanh so do cua 2 goc A va A\(_1\)
b, cho 2 tam giac ABC va A\(_1\)B\(_1\)C\(_1\) co AB=A\(_1\)B\(_1\), AC=A\(_1\)C\(_1\) va A >A\(_1\).Chung minh rang BC > B\(_1\)C\(_1\)
giup di mk dang can gap!