If the magnitue of sum two vectors is equal to the magnitude of difference of the two vectors, the angle between these vectors is :-

Options

A. `60^(@) `
B. `90^(@)`
C. `105^(@)`
D. `120^(@)`

Answer

4

Explanation

`R= 2a cos (theta//2) rArr a = 2a cos (theta//2)`
`rArr cos (theta//2) = 1//2 rArr theta//2 = 60^(@) rArr theta = 120^(@)`