Question

find the cosine of the angle between the vectors a= i -2j+k and b=2i-2j+2k​

Answer 1

Answer:

$cosx = \frac{2 + 4 + 2}{\sqrt{6} \sqrt{8} } \\ cosx \: = \frac{8}{4 \sqrt{3 } } \\ cosx \: = \frac{2}{ \sqrt{3} }$

Answer 2

Answer:

we know that

dot product of vector A and B = mod(A)(mod(B)cosA

1*2 + (-2)*(-2) + 1*2 = (√(1+4+1)(√4+4+4 cosA

2 + 4 + 2 = √6*√12cosA

8 = 6√2 cosA

cosA = 8/6√2

cosA = 2√2/3