Question

If `|vec(A)+vec(B)|=|vec(A)|=|vec(B)|` then the angle between `vec(A)` and `vec(B)`is
A. `60^(@)`
B. `0^(@)`
C. `120^(@)`
D. `90^(@)`

Answer 1

Correct Answer - C
`R^(2)=A^(2)+B^(2)+2ABcos theta`
`"We have" R=A=B`
`So, " " A^(2)=A^(2)+2A^(2) cos theta`
`rArr" " cos theta =-(1)/(2)`
`rArr " " theta=120^(@)`