If the angle `alpha` between two forces of equal magnitude is reduced to `(alpha-pi//3),` then the magnitude of their resultant becomes `(alpha-pi//3),`times of the earlier one. The angle `alpha` is

Options

A. `pi//2`
B. `2pi//2`
C. `pi//4`
D. `4pi//5`

Answer

B

Explanation

`sqrt(F^(2)+F^(2)+2F^(2)cos(alpha(pi)/(3)))=sqrt3xx[sqrt(F^(2)+F^(2)+2F^(2)cosalpha)]`
on solving `,alpha=(2pi)/(3)" ""]"`