The magnitude of resultant of the two vectors of magnitude $4$ and $3$ is $1$. The angle between them is:

The correct option is A $\pi$
Given two vector A=4 and B=3 and the resultant is 1.

We have the formula $R=\sqrt{A^2+B^2-2\times A.B.cos\theta }$

So, $1=\sqrt{4^2+3^2-2\times 4\times 3\times cos\theta }$

$\pm 1=25-24cos\theta$

Taking +1 we get:-

$cos\theta =\frac{24}{24}$

$cos\theta =1$

$\theta =\pi$