Răspuns:
<BCD=75 de grade
Explicație pas cu pas
<DCA=<BAC=42
42=2/5* m<ABC
deci 42*5=2m<ABC
m<ABC=42*5/2=21*5=105 grade
in trg ABC suma unghiurilor =180
42+105+<ACB=180
147+<ACB=180
<ACB=180-147
<ACB=33 grade
<BCD=<BCA+<ACD=33+42=75 de grade
