Question

Keeping one vector constant, if direction of other to be added in the first vector is changed continuously, tip of the resultant vector describes a circles, In the following figure vector `vec(a)` is kept constant. When vector `vec(b)` addede to `vec(a)` changes its direction, the tip of the resultant vector `vec(r)=vec(a)+vec(b)` describes circles of radius b with its centre at the tip of vector `vec(a)`. Maximum angle between vector `vec(a)` and the resultant `vec(r)=vec(a)+vec(b)` is

A. `tan^(-1)""((b)/(r))`
B. `tan^(-1)""((b)/(sqrt(a^(2)-b^(2))))`
C. `cos^(-1)(r//a)`
D. `cos^(-1)(a//r)`

Answer 1

Correct Answer - A::C
Angle between `vec(r)` and `vec(b)` is maximum when `vec(r)` is tangent to circle.