Question

The resultant of two vectors 2N and 3N is square root 19N. The angle between the forces is

Answer 1

$R= \sqrt{ P^{2}+ Q^{2} +2PQcos \alpha }$
$\sqrt{19}$=$\sqrt{4+9+12cos \alpha }$
cos$\alpha$= 1/2
⇒ $\alpha$ = 60°

Answer 2

$R^2=A^2+B^2+2ABcos \beta \\ cos \beta =(R^2-A^2-B^2)/2AB \\ cos \beta =(19-4-9)/(2\times 2\times 3)=1 /2 \\ \beta = 60 degrees$