exercitiu 3 (b) urgent,dau coroana

un trapez isoscel are unghiurile de la baza congruente
=> m(∡A) = m(∡D)
stim ca m(∡B) + m(∡C) = 220°
=> m(∡A)+m(∡B) == 360 - 220 = 140 °
=> m(∡A) = m(∡D) = 70°
dar m(∡B) + m(∡C) = 220°
m(∡B) = m(∡C) => m(∡B) = m(∡C) = 110°