Vector a =1 vector b= 1 Vector R = 1 then
R^2 = a^2 + b^2 + 2 a b cos theta
Thus
1 = 1 +1 + 2.1.1.cos.theta
2cos theta = -1
Cos theta = -1/2
Theta = 120 degree
1
Manaswani answered this
Let vectors A and B inclined at an angle P.
The resultant is given by A+B and we know that magnitude of resultant is 1. So,
(A+B)= A²+B²+2AB cos P
1 =1 + 1 + 2 cos P
By solving further we get : P= 120.
Therefore angle / theta = 120.