ABCD - paralelogram⇒ ∡A≡∡C si ∡B≡∡D
∡A+∡D=180 si ∡C+∡D=180
a) D*15/9 = A*25/10
D*5/3 = A*5/2⇒ 5D/3 = 5A/2⇒D/3 = A/2 = k
D=3k si A=2k
3k+2k=180
5k=180
k=180:5=36 ⇒ D=3 * 36=108° si A = 2*36=72°
∡A≡∡C = 72° si ∡B≡∡D=108°
b) C*1/3 = D*1/7⇒ C/3=D/7=k
C=3k si D=7k
3k+7k=180
10k=180
k=180:10
k=18
C=3*18=54 si D= 7*18=126
∡A≡∡C = 54° si ∡B≡∡D=126°