Vă rog, răspunsul complet v-a primi corana.

[tex]\it BD\ -\ diametru\ \Rightarrow m(\widehat{BCD})=90^o\\ \\ \Delta ABC\ -\ echilateral\ \Rightarrow\ m(\widehat{BCA})=60^o\\ \\ m(\widehat{ACD})= m(\widehat{BCD})- m(\widehat{BCA})=90^o-60^o=30^o[/tex]