Question

The magnitude of A - B vector is A + B. Then the angle [in
radian] between A and B vector is

a.π/2

b.3π/2

c.5π/2

d.π​

Answer 1

Answer:

(D)

Explanation:

let

magnitude of A = a

magnitude of B = b

angle between vectors = x

A-B=a+b

$\sqrt{ {a}^{2} + {b}^{2} - 2ab \cos(x) } = a + b \\ {a}^{2} + {b}^{2} - 2ab \cos(x) = {(a + b)}^{2} \\ {a}^{2} + {b}^{2} - 2ab \cos(x) = {a}^{2} + {b}^{2} + 2ab \\ \cos(x) = - 1 \\ x = {180}^{o} = {\pi}^{c}$