Question

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

Answer 1

Explanation:

A=i+2j-k

b=-i+j-2k

as we know that,for two given vectors a

and b,we have:-

a.b=|a|*|b|*cos a^b

where a^b is the angle between the vectors

a and b

so, a.b= 1*-1+2*1+-1*2=3

|a|=(1+4+1)^1/2=√6

|b|=(1+1+4)^1/2=√6

from the given equation,we have

3=√6*√6*cos a^b

so,cos a^b=3/6=1/2

so angle between the vectors is 60 degree