|vector{p}|=sqrt(4^2+2^2+3^2)=sqrt(29)
vector{q}=2vector{a}-vector{c}=(-4+2;6-1;-4+3)=(-2;5;-1)
|vector{q}|=sqrt((-2)^2+5^2+(-1)^2)=sqrt(30)
cos∠ (vector{p},vector{q})=vector{p}*vector{q}/(|vector{p}|*|vector{q}|) =
=(4*(-2)+2*5+3*(-1))/sqrt(29)*sqrt(30)=-1/(sqrt(29)*sqrt(30))
∠ (vector{p},vector{q})=arccos(-1/(sqrt(29)*sqrt(30)))