1) vector{BD}*vector{AC}=0, так как BD⊥AC.
2) AB=BC=2
BD=sqrt(2)
vector{BD}*vector{AC}= |vector{BD}|*|vector{AC}|*cos45 градусов=
=sqrt(2)*2*sqrt(2)/2=2
3) vector{BD}*vector{BD}= |vector{BD}|*|vector{BD}|*cos0 градусов=
=sqrt(2)*sqrt(2)*1=2