anther doubt in quadratic eq

if     and  are da roots of 4x² +2x-1=0 then  =

a) -18degrees   b)18    c)36  d)54

anyone plzzzzzzzz reply plzz

The given quadratic can be written as (2x+1/2)²=5/4

So,the roots of the eqn. are rt5-1/4 and -(rt5+1/4) which are sin18⁰ and sin(-54⁰) respectively.So,the value of   can only be 18⁰ and k=-3.

If u check the other options,u see that it can't be 36⁰,it can't be -18⁰ bcoz 1-rt5/4 is not a root and similarly can't be 54⁰.

So,I think the ans is option (B).