[tex]\it AD - minim\breve a \Rightarrow AD\perp BC \Rightarrow\Delta DBA-dreptunghic,\ \hat D=90^o\ \ \ \ \ (1) \\ \\ \hat B=60^o\ \ \ \ \ (2)\\ \\ (1),\ (2) \Rightarrow \widehat{BAD}=30^o\ (complementul\ lui\ 60^o)\\ \\ \widehat{DAC}=\widehat{BAC}-\widehat{BAD}=40^o-30^o=10^o[/tex]
