Question

If the magnitude of a + b is equal to a minus b then a and b are perpendicular vectors how

Answer 1

Note: the quantities are vectors, but not indicated with an arrow or bold-typeface - on mobile.

|a + b| = |a - b|

Squaring both the sides, we get:

a² + b² + 2a.b = a² + b² - 2a.b

Hence, 4a.b = 0

Or, clearly, a.b = 0, which implies the vectors are perpendicular.