m(∡ACD)=70°=> m(∡CAD)=70°
in ΔACD:
m(∡ADC)=180°-m(∡ACD)-m(∡CAD)
m(∡ACD)=180°-70°70°
m(∡ACD)=40°
daca ABCD este romb=> m(∡ACD)=m(∡ABD)=> m(∡ABD)=40°
daca ABCD este romb=> ΔABC isoscel=> m(∡BAC)=m(∡BCA)
m(∡BCA)=[180°-m(∡ABC)]:2
m(∡BCA)=(180°-40°):2
m(∡BAC)=140°:2=> m(∡BCA)=70°
daca m(∡BCA)=m(∡BAC)=>m(∡BAC)=70°
m(∡BAD)=m(∡BAC)+m(∡CAD)
m(∡BAD)=70°+70°
m(∡BAD)=140°
m(∡BCD)=m(∡BCA)+m(∡ACD)
m(∡BCD)=70°+70°
m(∡bcd)=140°
mai este o rezolvare mai pe scurt
