a) Trong \(\Delta BHE,\widehat{BHE}=90^o\) có:
\(\Rightarrow BE>BH\left(ch>chv\right)\left(1\right)\)
b) Trong \(\Delta CEK,\widehat{CEK}=90^o\) có:
\(\Rightarrow CE>CK\left(ch>chv\right)\left(2\right)\)
Từ (1) và (2) \(\Rightarrow BE+CE>BH+CK\)
\(\Rightarrow BC>BH+CK\)