Question

The angle between the vectors ( i - j ) and ( i + j ) is _ , where i and j are the unit vectors along X and Y axis

Answer 1

Answer:

90°

Explanation:

Let A= i - j and B = i + j

| A | = √ { 1^2+ (-1)^2 = √2

| B | = √{1^2 + 1^2} = √2

A . B = | A | | B | cos ©

( i - j ) . ( i + j ) = √ 2 × √2 cos ©

i.i + j.i - j.i - j.j = 2 cos ©

1 - 1 = 2 cos ©

cos © = 0

cos © = cos 90°

and hence angle (©) = 90°