Question

Two vectors

A and B

 

have equal

magnitudes. If the magnitude of

A + B

 

is

equal to n times the magnitude of

A - B

 

,

Then the angle between

A and B

 

is​

Answer 1

Answer:

I hope a+b is correct answer

Answer 2

Answer:

${a}^{2} + {b}^{2} + 2ab \cos( \alpha ) = n( {a}^{2} + {b}^{2} - 2ab \cos( \alpha ) )$

as a=b=x

solving

$2 {x}^{2} + 2 {x}^{2} \cos( \alpha ) = 2n {x}^{2} - 2n {x}^{2} \cos( \alpha )$

$\cos( \alpha ) (n + 1) = (n - 1)$

$\alpha = { cos}^{ - 1} ( \frac{n - 1}{n + 1} )$