Fie ABCD un patrulater convex.Dacă :
a) m(A)= 55 (grade), m(B)=75(grade) si m(C)= 120(grade),aflati m(D)
b)m(B)=83(grade),m(C)=90(grade) si m(D)=102(grade),aflati m(A)
c)m(C)=67(grade),m(D)=110(grade) si m(A)= 81(grade),aflati m(B)
d)m(D) =115(grade),m (A)= 70(grade) si m(B) =54(grade),aflati m(C)