Răspuns :
m(∡A)=2m(∡B)
m(∡A)+m(∡B)=180°
m(∡B)+2m(∡B)=180°
3m(∡B)=180°
m(∡B)=60°
m(∡B)= m(∡D)=60°
m(∡A)+m(∡B)=180°
m(∡B)+2m(∡B)=180°
3m(∡B)=180°
m(∡B)=60°
m(∡B)= m(∡D)=60°