Question

Fie A,B,C,D patru puncte astfel incat [AB] ≡ [BC] ≡ [CD] ≡ [DA]
Aratati ca ∢ABC ≡ ∢ADC si ∢BAD ≡∢ BCD.

Answer 1

[AB]≡[BC]≡[CD]≡[DA]=> ABCD-patrulater cu AB=BC=CD=DA => masura     
 ∢ABC=90 grade

∢ABC=90 grade 
ABCD-patrulater ....din cele doua rezulta ca ∢ABC≡∢ADC≡∢BAD≡∢BCD.