Скалярное произведение векторов

a*b =|a|*|b|*cos(a,b)

1) a*b =4√3*√3/2 =6

2) 40*cos(a,b) =20 <=> cos(a,b)=1/2 <=> ∠(a,b)=60°

3) 7b*√2/2 =7 <=> b=√2

4) 0,01*9,01*cos(a,b) =0 <=> cos(a,b)=0 <=> ∠(a,b)=90°

5) a*2*(-1/2) =-3 <=> a=3

6) a*b =6√2*(-√2/2) = -6

7) 4√3*cos(a,b) =-6 <=> cos(a,b)= -√3/2 <=> ∠(a,b)=150°