3.
a.
Do \(\Delta ABC=\Delta HIK\) nên \(AC=HK\)
Mà \(HK=7cm\) suy ra \(AC=7\left(cm\right)\)
b.
Chu vi tam giác ABC là:
\(AB+BC+AC=7+8+7=22\left(cm\right)\)
Do \(\Delta ABC=\Delta HIK\) nên chu vi tam giác HIK bằng chu vi tam giác ABC
Suy ra chu vi tam giác HIK là 22 (cm)
4.
a.
Do \(\Delta ABC=\Delta DMN\) nên \(\left\{{}\begin{matrix}\widehat{A}=\widehat{D}\\\widehat{B}=\widehat{M}\\\widehat{C}=\widehat{N}\end{matrix}\right.\)
Mà \(\widehat{M}=60^0\) suy ra \(\widehat{B}=60^0\)
Theo tính chất tổng 3 góc trong tam giác ABC:
\(\widehat{A}+\widehat{B}+\widehat{C}=180^0\)
\(50^0+60^0+\widehat{C}=180^0\)
\(\widehat{C}=180^0-50^0-60^0=70^0\)
b,
Do \(\widehat{A}=\widehat{D}\) mà \(\widehat{A}=50^0\) nên \(\widehat{D}=50^0\)
Do \(\widehat{C}=\widehat{N}\) mà \(\widehat{C}=70^0\) nên \(\widehat{N}=70^0\)