A vector `vec(a)` is turned without a change in its length through a small angle `d theta`. Find the value of `|Deltavec(a)|` and `Delta a`.

Options

A. `0, a dtheta`
B. `a.d theta,0`
C. `0,0`
D. None of these

Answer

B

Explanation

(b) `|Deltaa|=sqrt(a^(2)+a^(2)-2a.a.cos (dtheta))=2a sin ((dtheta )/(2))`
for small angles sin `(dtheta)/(2) ~~dtheta)/(2)`
`|Deltaa|=2axx(dtheta)/(2) =a.dtheta`