Question

sa se afle aria unui paralelogram ABCD in care stim ca AC⊥CB, AB=4cm si m(<D)=45 de grade.

Answer 1

m(∡B)=m(∡D)=45 grade (∡ op in paralelg)
⇒ΔACB dr isoscel
in ΔABC dr isos aplicam teo lui Pitagora si obtinem
AC²+BC²=AB², 
dar AC=BC
deci 2AC²=16
AC²=8
⇒AC=√8=2√2
Aria ΔABC= AC*BC/2= 2√2*2√2/2=4 cm²

dar ΔCAD= ΔACB
⇒Aria ABCD=Aria ΔACD + Aria ΔABC=2*Aria ΔABC= 2*4= 8 cm²

O seara buna!