Two equal vector have a resultant equal to either of them, then the angle between them will be:

Options

A. `60^(@)`
B. `90^(@)`
C. `100^(@)`
D. `120^(@)`

Answer

D

Explanation

(d): Resultant of two vectors R=A
`:. A^(2)+B^(2)+2AB cos theta =A^(2)`
Vectors are equal, A=B
`2B^(2)+2B^(2) cos theta =B^(2)`
`2B^(2) cos theta =-B^(2)`
`cos theta =-(1)/(2)`
`theta=120^(@)`