Question

the angle between vector a = i + j and b = i - j is​

Answer 1

Explanation:

Angle between 2 vectors is defined by

cos∅ = a.b/ |a| × |b|

in this case

cos∅ = (i+j) . (i-j) / √2 ×√2

since their dot product is zero ,

cos∅=0 and ∅ = 90°