Răspuns :
unghiurile opuse sunt congruente
<B≡<C
<A≡<C⇒<A=142/2=71 grade
<C=71 grade
<B≡<D=x
71+x+71+x=360
2x+142=360
2x=360-142
x=218/2
x=109
<B=109 grade
<D=109grade
<B≡<C
<A≡<C⇒<A=142/2=71 grade
<C=71 grade
<B≡<D=x
71+x+71+x=360
2x+142=360
2x=360-142
x=218/2
x=109
<B=109 grade
<D=109grade