найдите скалярное произведение векторов a и b 1) a = (a;b)b = (a;b)2) a = (a;b), b = (-a;-b)​

1)а(2;-1;4),b(3;2;-1)

ab=2*3+(-1)*2+(-1)*4=6-2-4=0

0

2)|a|=3,|b|=4,cos (a^b)=1/6

cos(a^b)=ab/|a|*|b|

1/6=ab/12

ab=12/6=2

2