Question

Daca ABCD-trapez isoscel cu laturile; AB= 5dm, AD=7 dm, CD=12 dm, BC=7 dm, cum determinam masurile unghiurilor?

Answer 1

AD = BC => ABCD isoscel

duc BF ⊥ CD

FC = (CD - AB ) : 2 = (12 - 5) : 2 = 7/2 = 3, 5 dm

In ΔBCF

sinC = CF/BC = 3,5/7 = 1/2  } => ∡C = 60°

dar cos60° = 1/2

ABCD isoscel => ∡C = ∡D = 60°

∡C + ∡B = 180 => ∡B = 180° - 60° = 120°

ABCD isoscel => ∡A = ∡B = 120°