Ex12/150-manual de clasa a 8-a Punctele A, B, C aparţin unui cerc în această ordine. Aflaţi:
a) m( ( AB), dacă m( (ACB)=100°;
b)m( (ACB),dacă m( (AB)=140°;
c)m( (AC), dacă m( (ABC)=25°;
d)m( (BC),dacă ( AB= (BC= ( AC.
Ex13/150
aflați măsură a a unghiului (O este centrul cercului):

Given: lines a and b are parallel and line c is a transversal. prove: 2 is supplementary to 8 what is the missing reason in the proof? statement reason 1. a || b, is a transv 1. given 2. ∠6 ≅ ∠2 2. ? 3. m∠6 = m∠2 3. def. of congruent 4. ∠6 is supp. to ∠8 4. def. of linear pair 5. ∠2 is supp. to ∠8 5. congruent supplements theorem corresponding angles theorem alternate interior angles theorem vertical angles theorem alternate exterior angles theorem