Question

If A_= B_+C_ and magnitudes of A_,B_,C_ are 5,4,3 unit respectively ,then angle between A_and B_ is

Answer 1

Answer: 90°

Explanation:

It is given that

$\frac{}{A} = \frac{}{B} + \frac{}{C}$

and

$\frac{}{A}$ = 5

$\frac{}{B}$ = 4

$\frac{}{C}$ = 3

From Parallelogram Law of vectors,

$\frac{}{B} + \frac{}{C} = \sqrt{B^{2}+{C^{2}+ 2BCcosθ }$

$5=\sqrt{4^{2} + 3^{2} + 2*4*3*cosθ }$

25 = 16 + 9 + 24cosθ

24cosθ = 0

cosθ = 0

∴ θ = 90°